US clinical trial statistics

175,638

US clinical trials indexed

24,857

recruiting now (14% of total)

28,708

distinct conditions studied

15,742

sponsoring organizations

52

states & territories with sites

Key findings

What the registry does not report about itself, computed across all 175,638 indexed trials as of 2026-08-08. Every line carries its own denominator so it can be quoted as it stands.

1. Most conditions are studied by exactly one trial.

   17,338 of the 28,708 conditions in the registry (60.4%) carry a single registered study. Research attention is spread across a very long tail, not concentrated in a few hundred well-covered diseases.

2. One hundred sponsors run half of all the research.

   The 100 most active of 15,742 sponsoring organizations account for 88,635 trials, or 50.5% of the registry. At the other end, 8,355 sponsors appear on exactly one trial.

3. The typical trial is small.

   Median target enrolment is 60 participants. 107,618 of the 173,461 trials that report a genuine target (62%) plan to enrol fewer than 100 people.

4. Roughly one trial in seven is open to new participants.

   24,857 of 175,638 trials (14.2%) are recruiting. The remainder have finished, stopped early, or have not opened enrolment yet, which is why a raw registry search returns mostly closed studies.

5. Phase 2 trials stop early most often.

   16.4% of Phase 2 trials (5,153 of 31,395) were terminated, against 12.1% of Phase 3 trials. Termination is recorded by the sponsor and covers recruitment failure as well as safety and futility stops.

6. Trial sites cluster in five states.

   Of the 60,823 trials that list a US facility, 34,096 (56.1%) run at least one site in California, Florida, New York, Texas and Massachusetts. Trials without a listed facility are excluded from this figure rather than counted as zero.

7. Half the registry carries no usable phase label.

   59,069 trials are marked not applicable and 27,508 record no phase at all, together 49.3% of the registry. 59,157 of them are interventional studies rather than observational ones, so filtering a registry search by phase drops a large block of drug and device trials along with the observational ones.

Trials by phase

Of the 175,638 indexed trials, the largest reported phase is Phase 2. The "not applicable" bar is the biggest one, and as the finding above shows, 59,157 of those trials are interventional rather than observational. According to ClinicalTrials.gov, phase is self-reported by each study's sponsor.