A clinical research organisation (CRO) is a company that runs clinical trials on behalf of pharmaceutical, biotech, and medical-device firms. The largest global CROs — including IQVIA, ICON, Fortrea, Parexel, and Labcorp — manage trials worldwide but rarely recruit the public directly. If you want to take part in a paid UK study, the organisations that actually recruit volunteers are dedicated early-phase units such as Hammersmith Medicines Research and Richmond Pharmacology.
This guide explains who the main players are, the crucial difference between a CRO that runs trials and a unit that recruits you, and how to tell a reputable provider from one to avoid.
What is a CRO, in plain English?
A CRO (contract research organisation) provides the people, sites, and systems to carry out clinical trials for the companies developing new treatments. Drug and device developers hire CROs because building that capability in-house is slow and expensive.
Under UK rules, any organisation carrying out trial functions must comply with good clinical practice and is subject to inspection by the MHRA. Trials must also be approved by an ethics committee overseen by the Health Research Authority. That regulatory backbone is what makes a legitimate trial safe to join, whichever company is running it.
The key distinction most guides miss
There are two very different types of company people lump together as “clinical trial companies”:
- Global CROs design and manage trials for pharma clients across many countries. They are enormous, but they generally don’t advertise for members of the public to walk in. Examples: IQVIA, ICON, Fortrea, Parexel, Labcorp.
- UK early-phase clinical research units run trials in their own facilities and actively recruit paid healthy volunteers. This is where most people who want to take part — and get paid — should be looking. Examples: Hammersmith Medicines Research (HMR) and Richmond Pharmacology.
If your goal is to participate, focus on the second group. If you’re simply researching the industry, the first group is who you’ll read about most.
Top clinical research organisations compared
| Organisation | Type | Focus | Recruits the public directly? |
|---|---|---|---|
| IQVIA | Global CRO | Full-service trials, data and analytics across many countries | Rarely — works via sponsors and sites |
| ICON plc | Global CRO | End-to-end trial management, all phases | Rarely |
| Fortrea | Global CRO | Full clinical development (spun out of Labcorp in 2023) | Rarely |
| Parexel | Global CRO | Trial management, regulatory and consulting | Occasionally, via its own units |
| Labcorp | Global CRO / lab services | Testing, diagnostics, drug development | Rarely |
| Hammersmith Medicines Research (HMR) | UK Phase 1 unit | Early-phase trials in healthy volunteers, London | Yes — recruits paid volunteers |
| Richmond Pharmacology (Trials4us) | UK Phase 1 unit | Early-phase and specialist trials, London | Yes — recruits paid volunteers |
| MAC Clinical Research | UK trials group | Multiple UK sites, patient and volunteer studies | Yes — recruits volunteers |
Details reflect each organisation’s publicly stated focus and can change; always check the provider’s current information before applying.
A closer look at the units that recruit UK volunteers
Hammersmith Medicines Research (HMR) is one of the UK’s largest early-phase units, based in London and running trials in healthy volunteers since 1993. It holds MHRA Phase 1 accreditation and operates purpose-built facilities with resident medical cover. It recruits healthy adults for paid studies and is a genuine option for people who want to take part.
Richmond Pharmacology, which recruits volunteers through its Trials4us programme, runs its clinical research unit near London Bridge. It carries out trials for the pharmaceutical industry and is inspected by the MHRA. It actively recruits healthy volunteers for paid medical research.
MAC Clinical Research operates trial sites across the UK and recruits both patients and healthy volunteers. We’ve reviewed it separately in our guide to whether MAC Clinical Research is legit.
How to choose a reputable provider
Whichever organisation you consider, the same signals separate the trustworthy from the questionable:
- MHRA authorisation and inspection. Reputable UK units run MHRA-authorised trials and are inspected for good clinical practice.
- Ethics approval. Every study should have approval from a research ethics committee via the HRA.
- Clear informed consent. You should get full written information and time to ask questions before agreeing, and be free to withdraw at any point, in line with NHS guidance.
- No fees to join. Legitimate trials pay you; they never charge you.
- A track record you can check. Established units publish results and have a visible history.
You can also search live, approved UK studies directly through the NHS-backed Be Part of Research service, which lists trials by condition and location.
How CheckMyTrial helps
We compare providers so you can see who runs what, who recruits, and who pays — without wading through corporate jargon. If you’re weighing up specific companies, our review of whether Fortrea is legit and our look at whether GoodLab Group is legit are good next reads.
If your priority is earning, see our guide to paid clinical trials in the UK and how getting paid for clinical trials works. To understand your protections, read our overview of clinical trial safety and compensation, and when you’re ready to act, our guide to finding the best clinical trials and our clinical trials FAQ will point you in the right direction.
FAQ’s
What does CRO stand for?
CRO stands for clinical research organisation (also called a contract research organisation). It’s a company that runs clinical trials on behalf of the pharmaceutical, biotech, and medical-device companies developing new treatments.
Which are the biggest clinical research organisations?
The largest global CROs include IQVIA, ICON, Fortrea, Parexel, and Labcorp. These manage trials worldwide for pharma clients but generally don’t recruit members of the public directly.
Which UK companies recruit paid clinical trial volunteers?
Dedicated early-phase units such as Hammersmith Medicines Research (HMR) and Richmond Pharmacology actively recruit paid healthy volunteers in the UK. MAC Clinical Research also recruits volunteers across several UK sites.
Are UK clinical research organisations regulated?
Yes. Any organisation running clinical trials in the UK must comply with good clinical practice, is subject to MHRA inspection, and can only run trials approved by a research ethics committee overseen by the Health Research Authority.
Do I have to pay a CRO to take part in a trial?
No. Legitimate clinical trials pay participants for their time and reasonable expenses. You should never be asked to pay a fee to join a study — that’s a warning sign.
How do I find approved clinical trials in the UK?
You can search approved UK studies by condition and location through the NHS-backed Be Part of Research service, or compare providers using CheckMyTrial before you apply.
This article is general information about clinical research organisations and is not medical guidance. Speak to your GP before deciding whether a clinical trial is right for you, and always read trial documentation carefully before giving consent.