ClinicalTrials.gov

ClinicalTrials.gov is the NLM-operated (NIH, with FDA) public registry and results database for clinical studies, distinguished from clinical trial registration generally by being the specific U.S. system launched in 2000 (FDAMA Sec. 113) whose mandatory-registration and results-reporting requirements were established by the FDAAA 801 final rule (effective 18 January 2017), and which assigns every registered study a unique NCT identifier.

ByCASRAI Editorial Board

· Last updated 17 Jul 2026

Worked examples

Is an instance

A pharmaceutical sponsor registers a Phase 2 drug trial on ClinicalTrials.gov within 21 days of enrolling its first participant, then posts summary results within 12 months of primary completion.

Is an instance

A manuscript submitted to an ICMJE-member journal cites its ClinicalTrials.gov NCT number so editors and readers can confirm prospective registration.

Looks similar, but isn't

Not an instance

An NIH-funded behavioral study outside FDAAA's narrower 'applicable clinical trial' definition can still be required to register/report on ClinicalTrials.gov, but under the separate NIH dissemination policy, not FDAAA 801.

Not an instance

A trial registered only with a different WHO ICTRP primary registry (e.g. the EU's CTIS or India's CTRI) is still compliant under ICMJE's policy, which accepts any qualifying primary registry, not ClinicalTrials.gov exclusively.

ClinicalTrials.gov is the specific public registry and results database operated by the U.S. National Library of Medicine (NLM), part of the National Institutes of Health (NIH), in collaboration with the Food and Drug Administration (FDA). It is one named implementation of the broader concept of clinical trial registration — this entry covers the registry itself as a specific system (who runs it, what it legally requires, and how its identifiers work), not the general registration concept, which is covered on that term page.

What it is, specifically

ClinicalTrials.gov was established in February 2000 under Section 113 of the FDA Modernization Act of 1997 (FDAMA), initially as a registry of study identifying and design information. Its scope and legal weight expanded substantially with the FDAAA 801 (Food and Drug Administration Amendments Act of 2007, Section 801) final rule, which took effect 18 January 2017 and did two things: made registration mandatory (not just available) for a defined category of “applicable clinical trials” (ACTs), and added a companion results database requiring posted outcome data — participant flow, baseline characteristics, outcome measures, and adverse events — no later than 12 months after a trial’s primary completion date. A separate, broader NIH policy (effective the same date) layers additional results-reporting obligations onto every NIH-funded trial, not only FDAAA-defined ACTs.

ClinicalTrials.gov is also one of the World Health Organization’s recognized “primary registries” within the WHO International Clinical Trials Registry Platform (ICTRP) network — trials registered there are automatically discoverable through ICTRP’s global search alongside trials registered in other national/regional primary registries (e.g. the EU’s CTIS, ISRCTN, ANZCTR).

The NCT number

Every study record on ClinicalTrials.gov is assigned a unique identifier in the format NCT followed by an eight-digit number (for example, NCT00000419) — commonly called the “NCT number.” This is ClinicalTrials.gov’s own registry-specific identifier, distinct from the WHO’s voluntary Universal Trial Number (UTN), which exists independently to tie together records for the same trial across multiple national registries. The NCT number is what journals, funders, and manuscripts cite to unambiguously point to a specific trial’s registry record.

Who is responsible for a listing

The trial’s “responsible party” — typically the sponsor, or in some cases the principal investigator — is legally accountable for both registering the trial within the required window and submitting results on time. Under FDAAA 801, failure to comply can trigger a public FDA “Notice of Noncompliance” posted on ClinicalTrials.gov itself, followed by civil monetary penalties (a statutory base of up to $10,000 per day of continued violation after a remediation window), separate from any action a funding agency might separately take under its own grant terms.

Examples

A pharmaceutical sponsor registers a Phase 2 drug trial on ClinicalTrials.gov within 21 days of enrolling its first participant, satisfying FDAAA 801’s applicable-clinical-trial deadline, and later posts summary results within 12 months of the trial’s primary completion date.
A manuscript submitted to an ICMJE-member journal cites its ClinicalTrials.gov NCT number in the abstract, allowing editors and readers to confirm the trial was prospectively registered before enrollment began.

Counter-examples

A behavioral intervention study that is NIH-funded but does not meet FDAAA’s narrower “applicable clinical trial” definition (e.g., certain Phase 1 studies) can still be legally required to register and report on ClinicalTrials.gov — but through the separate NIH dissemination policy, not FDAAA 801. Citing only FDAAA 801 as the basis would misstate which rule actually applies.
A trial registered solely with a different WHO ICTRP primary registry (for example, the EU’s CTIS or India’s CTRI) is still a compliant, prospectively registered trial under ICMJE’s policy — it does not need a ClinicalTrials.gov listing specifically, since ICMJE accepts any qualifying primary registry, not ClinicalTrials.gov exclusively.

Related terms

See Clinical Trial Registration for the general concept this registry implements, and Prospective Clinical Trial Registration for the ICMJE timing rule. For the full compliance picture — FDAAA 801 vs. NIH policy vs. ICMJE, deadlines, and enforcement — see the Clinical Trial Registration and Reporting Compliance guide.

Use in your systems

JATS XML <role> element

xml

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Schema.org DefinedTerm (JSON-LD)

json

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