How many clinical trials are in each phase?
About half the 461,000 clinical trials registered on ClinicalTrials.gov as of September 2026, some 237,000, have no phase: phases describe drug trials, and these test devices, surgery, behavior or diet. Among drug trials, Phase 2 (does it work, and at what dose?) is the most common with about 66,000. Phase 1 tests safety in a few people, Phase 3 compares a treatment with the usual care in many, and Phase 4 follows a drug after approval.
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Source and date
- Data as of
- Published
The data
| Phase | Clinical trials (all years) |
|---|---|
| Early Phase 1 | 6,491 |
| Phase 1 | 48,715 |
| Phase 1/2 | 17,092 |
| Phase 2 | 65,627 |
| Phase 2/3 | 7,600 |
| Phase 3 | 42,314 |
| Phase 4 | 35,851 |
| No phase (devices, behavior, etc.) | 237,399 |