Diversity in clinical trials measures how closely a study's participants, by race, ethnicity, sex, and age, match the population that actually carries the disease under investigation, a distinct benchmark from the country's overall demographics that the FDA and Congress now regulate directly. Only 6% of 341 Phase III pivotal trials run between 2017 and 2023 achieved enrollment matching the four largest US racial and ethnic groups, according to a December 2025 study in Communications Medicine. This article compiles the current enrollment data by demographic group, explains what the FDA's Diversity Action Plan rule requires, and covers why the representation gaps persist even as reporting compliance has improved.
The state of clinical trial diversity in one table
Federal Drug Trials Snapshots reports and peer-reviewed studies published between 2023 and 2026 show that clinical trial enrollment has not matched US disease prevalence for every demographic group, despite more than a decade of federal reporting requirements. The table below summarizes the headline figures referenced throughout this article.
MetricFindingSourceYearTotal participants in 2025 approval trialsRoughly 26,000 participants across 46 novel drug approvalsFDA 2025 Drug Trials Snapshots Summary Report2025Total participants in 2024 approval trialsRoughly 31,000 participants across 50 novel drug approvals; female share ranged 9% to 98% by drug programFDA 2024 Drug Trials Snapshots Summary Report2024Total participants in 2023 approval trialsRoughly 44,000 participants across 55 novel drug approvalsFDA 2023 Drug Trials Snapshots Summary Report2023Pivotal trials matching US racial and ethnic demographicsOnly 6% of 341 Phase III pivotal trials (2017 to 2023) matched the four largest US racial and ethnic groupsCommunications Medicine (Nature), 20252025Oncology trial participation by raceBlack patients 4.4%, Hispanic/Latinx patients 4.2%, White patients 7.2% of eligible patients enrolled (2017 to 2022)JAMA Network Open, 20232023Adequate representation in oncology pivotal trialsReached in 82% of trials for women, 73% for Asian patients, 46% for adults 65 and older, 27% for Hispanic or Latino patients, 11% for Black patients (85 indications, 2015 to 2021)JAMA, 20232023
Representation has not caught up with the populations most affected by the diseases under study, across race, ethnicity, and age, even as reporting compliance itself has improved sharply.
Who actually enrolls in US clinical trials
The FDA's three most recent Drug Trials Snapshots reports count roughly 101,000 pivotal-trial participants across 151 novel drug approvals from 2023 through 2025, with sex balance varying widely by therapeutic area and persistent gaps by race, ethnicity, and age relative to disease burden.
In the FDA 2025 Drug Trials Snapshots Summary Report, roughly 26,000 participants took part in the pivotal trials supporting 46 novel drug approvals, and female participation across individual drug programs ranged from 9% to 99%. The 2024 report counted roughly 31,000 participants across 50 novel drug approvals, with female participation by program ranging from 9% to 98%, and the 2023 report covered roughly 44,000 participants across 55 novel drug approvals. The reports summarize sex by therapeutic area and exclude sex-specific indications, rather than publishing one aggregate split.
By race and ethnicity, the gap is sharper. A JAMA Network Open study published July 3, 2023 found that among eligible US oncology patients from 2017 to 2022, only 4.4% of Black patients (307 of 6,912) and 4.2% of Latinx patients (166 of 3,973) enrolled in a trial, compared with 7.2% of White patients (2,858 of 39,526). The adjusted hazard ratio for Black versus White trial participation fell from 0.61 in 2017 to 2019 to 0.49 in 2020 to 2022, meaning the participation gap widened rather than closed over the study period.
Age carries its own gap. A JAMA study published December 11, 2023 reviewed 85 FDA-approved oncology indications from 2015 to 2021 and found adequate representation, meaning enrollment proportional to disease burden, in 82% of trials for women, 73% for Asian patients, 46% for adults 65 and older, 27% for Hispanic or Latino patients, and 11% for Black patients. The same study found no statistically significant difference in clinical development time between adequately and inadequately represented trials.
Publicly funded research tells a different story. The NIAID FY2022-2024 Triennial Inclusion Report shows minority enrollment across NIAID-supported clinical research at 54.2% in FY2022, 61.0% in FY2023, and 71.7% in FY2024, with female enrollment rising from 45.4% to 49.3% over the same period. Black or African American enrollment at US sites was 17.0% in FY2022, split 26.6% female and 22.9% male in FY2023, and 14.1% female and 18.7% male in FY2024.
The gap between NIH-funded and industry-sponsored enrollment traces back three decades. The NIH Revitalization Act of 1993 first required NIH-funded research to include women and underrepresented racial and ethnic groups, but that mandate never extended to industry-sponsored trials, which produce most of the pivotal data behind drug approvals. FDORA, enacted in 2022, is the first statute to impose a comparable requirement on industry sponsors.
Enrollment versus disease prevalence: the representation gap
Even when a demographic group is present in a trial, its share is often smaller than its share of the people who actually have the disease being studied.
A Contemporary Clinical Trials Communications study published in April 2024 compared 17 US-only FDA approval trials from 2017 to 2020 against real-world prevalence data covering more than 150 million patients. Only 38 of 85 demographic cohorts studied, 45%, fell within the 0.75 to 1.25 ratio band researchers considered acceptable representation. Asian patients were underrepresented in 11 of the 17 trials, the most of any group studied, and Black or African American patients were underrepresented in 6 of the 17.
Population groupRepresentation gap vs. disease incidence or prevalenceSourceYearAsian patientsUnderrepresented in 11 of 17 FDA approval trials studied against real-world prevalence data (2017 to 2020)Contemporary Clinical Trials Communications, 20242024Black/African American patientsUnderrepresented in 6 of 17 FDA approval trials; participation ran 3 to 19 percentage points below disease incidence across 8 rare cancers (2004 to 2023)Contemporary Clinical Trials Communications, 2024; HHS ASPE Issue Brief, 20242024Hispanic/Latino patientsParticipation ran 33 to 52 percentage points below disease incidence across 8 rare cancers (2004 to 2023)HHS ASPE Issue Brief, 20242024All cohorts studied (aggregate)Only 45% (38 of 85) of demographic-cohort ratios fell within the acceptable 0.75 to 1.25 representation bandContemporary Clinical Trials Communications, 20242024
An HHS ASPE Issue Brief published October 16, 2024 found a similar pattern across 29,318 participants in 391 trials for eight rare cancers completed between 2004 and 2023. Hispanic or Latino participation ran 33 to 52 percentage points below disease incidence, and Black participation ran 3 to 19 percentage points below incidence, depending on the cancer studied.
The same ASPE brief found reporting practices have improved even where representation has not. Among the rare-cancer trials studied, race reporting rose from 38% for trials completed before April 2017 to 90% for trials completed after, and ethnicity reporting rose from 27% to 63%; April 2017 is when a federal requirement to report race and ethnicity data to ClinicalTrials.gov took effect. Accrual of participants from underrepresented groups in the National Cancer Institute's NCTN and NCORP networks rose from 14% in 1999 to 2001 to 25% in 2017 to 2019. Female participation in the rare-cancer trials still ran 15 percentage points below the FDA's own 2015 to 2019 Drug Trials Snapshots aggregate baseline.
What the FDA now requires: Diversity Action Plans
The Food and Drug Omnibus Reform Act, or FDORA, enacted in December 2022 as part of the Consolidated Appropriations Act, 2023, requires sponsors of certain drug, biologic, and device trials to submit a Diversity Action Plan to FDA ahead of a pivotal study. The requirement sits in section 3601 of FDORA, which added sections 505(z) and 520(g) to the Federal Food, Drug, and Cosmetic Act, and section 3602 directs FDA to issue guidance on the plans' format and content.
FDA published draft guidance describing what a Diversity Action Plan must contain on June 26, 2024, with a formal Federal Register notice published June 28, 2024. Under that draft, a plan must state enrollment goals broken out by age, sex, race, and ethnicity, the disease-prevalence or incidence data behind those goals, and the specific measures a sponsor will use to meet them. The public comment period on the draft guidance closed September 26, 2024.
The guidance's status has changed several times since. FDA removed the draft guidance from its website on January 23, 2025, following a presidential executive order on federal diversity, equity, and inclusion policy, according to a Crowell & Moring client alert. A federal judge ordered HHS, FDA, and CDC to restore the removed pages, and the Diversity Action Plan guidance was restored on February 11 to 12, 2025, following a ruling in Doctors for America v. Office of Personnel Management in the US District Court for the District of Columbia, reported by NPR and confirmed by Citeline/HBW Insight.
The litigation has since concluded. On July 3, 2025, the same court issued a final ruling that vacated the federal directives behind the removals and ordered the affected pages restored, as reported by Fierce Healthcare. As of mid-2026, the draft guidance remains posted on FDA's website, labeled a draft that is not for implementation and carrying a notice that the page was restored under court order. FDA has not issued a final version, despite a statutory deadline of June 26, 2025 for final guidance under FDORA. The underlying FDORA statutory requirement to submit a Diversity Action Plan remains in force throughout; only the guidance describing its expected form and content has been removed and restored.
Why representation gaps persist
Researchers most often point to four structural factors: trial-site geography, eligibility criteria, trust, and access and cost.
Pivotal trials concentrate at large academic medical centers, which are not evenly distributed relative to where underrepresented populations live, according to the HHS ASPE Issue Brief. A patient who lives hours from the nearest trial site faces a structural barrier to enrollment regardless of eligibility or interest.
Broad exclusion criteria, such as comorbidity limits, prior-treatment restrictions, and organ-function thresholds, screen out a larger share of patients from populations with higher rates of untreated comorbid conditions. FDA's November 2020 guidance on broadening eligibility criteria recommends designing trials to reflect the population expected to use the eventual approved drug, and it predates the FDORA Diversity Action Plan requirement. In December 2025, FDA reissued that guidance as Enhancing Participation in Clinical Trials, removing the word diversity from the title while keeping the recommendation to enroll trial populations that reflect the patients likely to take the drug if it is approved.
Trust is a documented factor in the clinical-trials literature: historical research practices have left some populations with a lower baseline willingness to enroll, independent of eligibility or access. Researchers treat trust as one of several contributing factors, not the primary driver.
Out-of-pocket costs remain a barrier even though the Affordable Care Act requires routine-care costs for trial participants to be covered; travel and childcare costs are not included in that requirement. The ASPE brief names these costs as a continuing access barrier separate from eligibility criteria. Sponsors track a related cost on their own side of the ledger: the per-patient cost and timeline impact of slow enrollment, which grows the longer a Diversity Action Plan's enrollment goals go unmet.
How trial design and channel choice shape who enrolls
Expanding where and how a trial recruits, more sites, decentralized or remote elements, translated materials, and community-based locations, changes who has practical access to enroll, independent of eligibility criteria.
Research on decentralized trial elements shows these changes most reliably widen geographic and site-level reach; evidence on whether they specifically close racial and ethnic representation gaps is still developing and mixed. Community-based and rural sites extend a trial's footprint beyond the academic medical centers where pivotal trials have historically concentrated. Multilingual materials remove a practical barrier for patients who would otherwise be excluded by language alone, independent of their eligibility on clinical grounds.
Community-based recruitment often runs through paid outreach and social channels, and what a sponsor or site can say to a prospective participant before enrollment even starts is bound by the IRB and platform rules that govern recruitment advertising. Those rules apply regardless of which demographic group a site is trying to reach.
Sponsors trying to close a demographic gap on a live trial rarely start from a blank page; many first look at how specialist agencies have solved site-diversity and channel mix on a comparable study. Eligibility criteria and site-selection choices set the outer bounds of who can enroll; channel and outreach choices determine who within those bounds actually hears about the trial.
What the data means for 2026 and 2027 trial planning
Reporting on clinical trial demographics has improved sharply since federal race and ethnicity reporting requirements took effect in April 2017: race reporting in the rare-cancer trials HHS studied rose from 38% to 90%. Representation itself, measured against both US demographics and disease-specific prevalence, has not kept pace with that reporting gain. The FDORA statutory requirement to submit a Diversity Action Plan has remained in force through the guidance's publication, removal, and court-ordered restoration, so sponsors building 2026 and 2027 trial designs should expect the requirement to bind eventually even without a final guidance document in place today.
Frequently asked questions
What does diversity in clinical trials mean?
Diversity in clinical trials means a study's participants, measured by race, ethnicity, sex, and age, reflect the population that actually has the condition under investigation, a different benchmark than the country's overall demographics. The FDA and Congress now require sponsors to plan for this explicitly as part of trial design.
What percentage of clinical trial participants are from underrepresented groups?
It varies widely by disease and group. A 2025 Communications Medicine study found only 6% of 341 Phase III pivotal trials (2017 to 2023) matched US racial and ethnic demographics, and just 23% adequately represented Black participants and 30% adequately represented Hispanic participants in 2023 trials specifically.
What is an FDA Diversity Action Plan?
A Diversity Action Plan is a document sponsors of certain drug, biologic, and device trials must submit to FDA under FDORA. It states enrollment goals by age, sex, race, and ethnicity, the disease-prevalence rationale behind those goals, and the specific measures the sponsor will use to meet them.
Is the FDA's Diversity Action Plan guidance currently in effect?
The FDORA statutory requirement to submit a Diversity Action Plan is in force. The draft guidance describing its expected form was published June 26, 2024, removed January 23, 2025, and restored February 11 to 12, 2025 by court order; a final ruling on July 3, 2025 vacated the removal directives. FDA has not finalized the guidance despite a June 26, 2025 statutory deadline.
Why are some racial and ethnic groups underrepresented in clinical trials?
Researchers most often point to four factors: trial sites concentrated at large academic centers, broad eligibility criteria that screen out common comorbidities, documented trust deficits tied to historical research practices, and out-of-pocket costs that persist despite ACA-mandated routine-care coverage for trial participants.