Most top CRO lists order the same names differently and never say why. Mergers, spin-offs and take-privates have also made last year's lists wrong, and size alone does not tell a sponsor who fits.
Contract research organizations are the companies sponsors hire to run clinical trial work. This guide ranks the largest by latest reported revenue, with the fiscal year and primary source beside every figure. A shortlist method follows for sponsors deciding which two or three to approach.
Top CRO companies in 2026 at a glance
By reported revenue, the five largest contract research organizations in 2026 are IQVIA, ICON, Thermo Fisher's PPD, Syneos Health and Labcorp, in that order. Syneos went private and stopped publishing accounts, so it sits fourth on its last audited figure (FY2022).
The table gives all ten. The note under it says which revenue line counts for each company.
| Rank | Company | Revenue line, fiscal year | HQ | Ownership | Known for |
|---|---|---|---|---|---|
| 1 | IQVIA | $8.90B, R&D Solutions segment, FY2025 | Durham, NC, US | Public (NYSE: IQV) | Phase I to IV trials plus a central lab |
| 2 | ICON | $8.25B, company total, FY2025 (restated basis) | Dublin, Ireland | Public (Nasdaq: ICLR) | Full-service Phase I to IV development |
| 3 | Thermo Fisher (PPD) | $7.92B, clinical research business, FY2025 | Waltham, MA, US (parent) | Subsidiary of Thermo Fisher (NYSE: TMO) | All phases plus site and patient access |
| 4 | Syneos Health | $5.39B, company total, FY2022 (latest audited) | Morrisville, NC, US | Private (Elliott, Patient Square, Veritas) | Clinical plus commercial services |
| 5 | Labcorp | $3.10B, Biopharma Laboratory Services segment, FY2025 | Burlington, NC, US | Public (NYSE: LH) | Central labs and preclinical testing |
| 6 | Fortrea | $2.72B, company total, FY2025 | Durham, NC, US | Public (Nasdaq: FTRE) | Trial management, clinical pharmacology |
| 7 | Medpace | $2.53B, company total, FY2025 | Cincinnati, OH, US | Public (Nasdaq: MEDP) | Clinical CRO for small and mid-size biotech |
| 8 | Charles River | $2.40B, Discovery and Safety Assessment segment, FY2025 | Wilmington, MA, US | Public (NYSE: CRL) | Preclinical (non-clinical) work |
| 9 | Tigermed | $0.96B (RMB 6,833M), company total, FY2025 | Hangzhou, China | Public (SZSE, HKEX) | Highest clinical CRO market share in China (company claim) |
| 10 | WuXi AppTec | $0.94B (RMB 6,719M), Testing plus Biology segments, FY2025 | Shanghai, China | Public (SSE, HKEX) | Preclinical testing and biology |
Revenue lines: the segment or business figures are IQVIA (R&D Solutions), Thermo Fisher (the "clinical research" line, shown before intrasegment eliminations), Labcorp (Biopharma Laboratory Services), Charles River (Discovery and Safety Assessment) and WuXi AppTec (WuXi Testing plus WuXi Biology). The company totals are ICON, Syneos Health, Fortrea, Medpace and Tigermed. Every figure is fiscal year 2025 except Syneos Health, which is FY2022. We converted Chinese figures from RMB at 7.129 per US dollar, the IRS 2025 yearly average exchange rate. The conversion is ours, not the companies'. Parexel is left unranked.
How we ranked the top CRO companies
We ordered companies by latest full-year reported revenue on the line closest to contract research services. Each figure comes from an SEC filing or a company investor release, and the fiscal year is named every time. Information is current to October 10, 2026.
Revenue measures scale and reach. It does not measure quality, speed or fit, which is why the specialists and shortlist sections come after the ranking.
Scale matters because sponsors outsource a large share of the work. IQVIA's FY2025 10-K estimates that about $75 billion of roughly $159 billion in addressable clinical development spending was outsourced in 2025, about 47% by our arithmetic. That is a company estimate of spend, not a count of trials.
Three recent shake-ups moved the order: the Fortrea spin-off from Labcorp, the Syneos Health take-private and PPD's absorption into Thermo Fisher.
The 10 largest contract research organizations, profiled
Core CRO services run from site management and monitoring to data management, biostatistics, regulatory work and central labs. The ten profiles follow the table order.
1. IQVIA
IQVIA leads on its Research & Development Solutions segment, the line that matters here. The segment reported $8,896M in FY2025, up 4.3%, in its Q4 2025 earnings release. The company's 10-K describes that segment as outsourced clinical research and clinical trial services, from Phase I to IV. On May 22, 2026 it bought certain European Discovery Services businesses from Charles River for a preliminary $125.2M in cash. From 2026 IQVIA re-segments, so next year's figure will not compare like for like.
2. ICON
Dublin-based ICON ranks second on total company revenue of $8,251.3M for FY2025, with no segment split. The result arrived late: an Audit Committee investigation into revenue recognition pushed the FY2025 release from February to May 27, 2026. Revenue was overstated by 0.8% in 2023 and 1.1% in 2024, so ICON is restating. Restated FY2024 revenue is $8,189.0M, so any list still citing the original $8.28B is out of date.
3. PPD (Thermo Fisher Scientific)
PPD is now a clinical research business inside Thermo Fisher. Its "clinical research" line was $7,915M in FY2025, against $7,836M in FY2024, per the Thermo Fisher 10-K. Because that figure is before intrasegment eliminations, read it as a ceiling. The business covers Phase I to IV plus site and patient access services. On March 24, 2026 Thermo Fisher completed its $8.875B cash acquisition of Clario, an endpoint data provider for trials.
4. Syneos Health
No current Syneos revenue figure exists. Elliott Investment Management, Patient Square Capital and Veritas Capital took Syneos Health private in September 2023 for about $7.1B including debt, and it stopped filing. The latest audited year is FY2022: $5,393.1M in total, of which Clinical Solutions was $4,070.6M. The company pairs clinical work with commercial services. On October 9, 2024 it named Costa Panagos CEO, who previously led IQVIA's R&D Solutions business.
5. Labcorp
Labcorp earns fifth place on a narrow slice. Its Biopharma Laboratory Services segment reported $3,098.2M in FY2025, up 6.0%, in the Q4 2025 release. That segment is central laboratory testing plus Early Development preclinical safety work. Since the Fortrea spin-off on June 30, 2023, Labcorp is not a full-service trial manager. On January 8, 2026 it sold its U.S. Early Development medical device testing portfolio to NAMSA.
6. Fortrea
Fortrea is the clinical development business Labcorp spun off on June 30, 2023, formerly Covance and Labcorp Drug Development. FY2025 revenue was $2,723.4M, per its 10-K. Fortrea sold Enabling Services in the second quarter of 2024, so all of that revenue came from clinical services. It offers Phase I to IV trial management, clinical pharmacology and consulting across more than 20 therapeutic areas. Anshul Thakral became CEO on August 4, 2025, after a $797.9M goodwill impairment in the first half of the year.
7. Medpace
Medpace is the pure-play clinical CRO on the list. Revenue reached $2,530.2M in FY2025, up 20.0% from $2,109.1M, according to its Q4 2025 release. It states particular strength in oncology, metabolic, cardiology, antiviral and anti-infective work, and it focuses on small and mid-size biotech. We found no ownership change for 2025 to 2026. Net book-to-bill slipped to 1.04x in Q4 2025, which management attributed to elevated cancellations on its earnings call.
8. Charles River Laboratories
Charles River Laboratories is here for scale, not for running trials. Its Discovery and Safety Assessment segment brought in $2,402.9M in FY2025 on a company total of $4,015.4M, per its Q4 2025 release. The work is preclinical (discovery, safety assessment, research models), so do not shortlist it for a late-phase study. After a strategic review it sold its CDMO and Cell Solutions businesses to GI Partners on May 6, 2026, and its European Discovery Services businesses to IQVIA on May 22.
9. Tigermed
Tigermed, based in Hangzhou, reports the highest market share among clinical CROs in China. FY2025 revenue was RMB 6,833M, about $0.96B, split between Clinical Trial Solutions (RMB 3,267M) and clinical-related and lab services (RMB 3,566M), per its 2025 annual results. The second group includes site management, data and lab work. The results release reports no ownership change; the notable item is a new global headquarters building in Hangzhou.
10. WuXi AppTec
WuXi AppTec closes the list as a preclinical and testing pick. On October 24, 2025 it signed to sell its China clinical CRO and site management units to Hillhouse. The release made the sale subject to government approvals. Its comparable line is WuXi Testing plus WuXi Biology: RMB 6,718.9M, about $0.94B. The company total is RMB 45.46B (about $6.38B), mostly small-molecule CDMO chemistry. Tigermed is within about 2% of it, so a different exchange rate could swap places 9 and 10.
Parexel: large, private and left unranked
Parexel is a large CRO that a revenue ranking cannot place honestly. It has not filed audited accounts since its 2017 take-private; the last audited total was $2,441.5M for FY2017, June year-end. Third-party estimates disagree by multiples and none is sourced, so we print none.
EQT IX fund and Goldman Sachs Asset Management bought Parexel from Pamplona for $8.5B in 2021. It offers Phase I to IV development, regulatory consulting and pharmacovigilance, and on April 29, 2026 it acquired Vitrana, an AI-enabled pharmacovigilance platform.
Specialist CROs the revenue ranking misses
Revenue gives you the top 10, while fit gives you a different list: the specialists bench. A global Phase I to IV giant can run a multi-country oncology program, while a device-only or early-phase CRO may suit a smaller study better.
Mid-size and specialist CROs worth a look:
- Worldwide Clinical Trials: full-service, with focus areas in rare disease, oncology, neuroscience, internal medicine and cell and gene therapy.
- Premier Research: oncology and hematology, neuroscience, rare disease, cell and gene therapy, pediatrics, plus MedTech.
- Caidya: leads with oncology and hematology, with cardiovascular-metabolic, neurology, immunology and rare disease.
- Celerion: early-phase work, including first-in-human dose escalation and bioequivalence studies.
Medical device sponsors have their own bench:
- NAMSA: MedTech testing, clinical and regulatory consulting since 1967.
- Avania: describes itself as a MedTech-only CRO.
- MCRA: device, diagnostics and biologics CRO, now part of IQVIA MedTech.
- Medpace's device and diagnostics group: a device practice inside a ranked clinical CRO.
Site geography is a fit factor too. Sites in the US, Europe including Germany, or Asia-Pacific change timelines. Sponsors planning for a trial population that mirrors real patients should ask where each CRO's sites actually sit.
How to choose a CRO partner from the top CRO companies
Picture a 40-person biotech about to start its first Phase II oncology study. The largest CRO may staff it with junior teams and rotating project managers, while a mid-size oncology specialist may put senior people on the study for the same budget. Neither is guaranteed; the checklist is how you find out.
Ask every shortlisted CRO about:
- Phase and therapeutic area: how many comparable studies it has run, and when.
- Site geography: where its sites and investigators are for your population.
- Study size and budget: whether your study is a priority or a small account.
- Senior attention: who leads the study day to day, and how often staff change.
- Quality system: audit history and how it handles protocol deviations.
- Recruitment scope: many contracts bundle patient recruitment, though some sponsors source participants separately through advertising that reaches eligible patients directly, which changes what you ask each CRO to price.
Request screen-failure and site-activation timelines on comparable studies, then judge the answers against published benchmarks for how fast trials actually enroll.
Outsourcing does not outsource everything. Under 21 CFR 312.3, a CRO assumes "one or more of the obligations of a sponsor" as an independent contractor, so the contract should spell out which obligations transfer and which oversight stays with you.
Next step: pick two or three CROs from the table or the specialists bench and send each the same checklist with your request for proposal.
Top CRO companies to work for
The biggest CROs hire the most, so clinical research professionals asking which CROs to work for usually end up looking at them. ICON, for example, reported approximately 40,100 employees as of December 31, 2025.
Experience varies by role, team and country, and no sourced pay dataset covers these companies, so this article prints no salary figures. Check current openings and employee reviews for the specific team you would join.
Frequently asked questions about CRO companies
Who are the big five CROs?
By reported revenue, the five largest CROs are IQVIA, ICON, Thermo Fisher's PPD, Syneos Health and Labcorp, in that order. IQVIA leads on its R&D Solutions segment, ICON on total revenue, PPD on Thermo Fisher's clinical research line, Syneos on its FY2022 audited total, and Labcorp on its central lab and preclinical segment.
What are the largest CRO companies in the United States?
Of the ten ranked, seven are headquartered in the US. They are IQVIA (Durham, North Carolina), PPD under Thermo Fisher (Waltham, Massachusetts), Syneos Health (Morrisville, North Carolina), Labcorp (Burlington, North Carolina), Fortrea (Durham), Medpace (Cincinnati) and Charles River (Wilmington, Massachusetts). Most run global site networks.
What is the difference between a CRO and a CDMO?
A CRO runs research and clinical trials for a sponsor; a CDMO develops and manufactures the drug itself. Some groups do both: Thermo Fisher runs pharma manufacturing services and the PPD clinical research business within the same segment.
Which CRO is best for a small biotech?
No single CRO is best. Small biotech sponsors usually do better shortlisting mid-size and specialist CROs that match their phase and therapeutic area, then testing how much senior attention the study will get. Medpace, which focuses on small and mid-size biotech, is one ranked example. Compare proposals on phase and therapeutic area, site geography, budget priority, senior attention, quality system and recruitment scope.