ClinicalTrials.gov is the free, public registry and results database for clinical studies, run by the US National Library of Medicine at the National Institutes of Health. Each registered study receives an NCT number.
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ClinicalTrials.gov
noun · clinical research
A public database of clinical studies, maintained by the US National Library of Medicine, holding study descriptions and, for many trials, summary results.
Related terms
In short
Explained
ClinicalTrials.gov exists to make clinical research visible. A record states the condition, the intervention, the design, eligibility criteria, locations, and the primary and secondary outcome measures that the trial pre-specified. Patients use it to find studies, researchers use it to see what is already under way, and reviewers use it to compare published results against what the trial said it would measure.
That last use is the main scientific argument for registration. When the outcomes are fixed in public before the data are in, it is harder to quietly switch the headline result afterwards. Journals following the ICMJE policy ask for registration in a public registry before the first participant is enrolled, and ClinicalTrials.gov is the most widely used one. Other registries exist, including national and regional ones; your funder or ethics committee may name a specific one.
In the United States, a federal law and its implementing regulation (42 CFR Part 11) require registration and results submission for "applicable clinical trials", a defined category that covers many, but not all, trials of drugs, biologics and devices. The deadlines commonly quoted are registration within 21 days after the first participant is enrolled and results within one year after the primary completion date, with provisions for delays and extensions. Whether your trial is covered, and the current deadlines, are questions for the current regulation and your regulatory team, so read the text rather than relying on a summary. Our ClinicalTrials.gov registration guide walks through the practical steps.
Registration draws on the protocol: title, purpose, design, arms and interventions, eligibility, outcome measures and sites. Results entries add participant flow, baseline characteristics, outcome data and adverse event tables. Having a clean protocol, defined endpoints and a well-kept adverse event log makes this much easier.
From trial data to registry
| Registry section | Source in your trial | Why it matters |
|---|---|---|
| Outcome measures | Protocol endpoints and the analysis plan | Pre-specified outcomes are the basis for spotting outcome switching |
| Enrolment and status | Screening and enrolment log | Status changes need timely updates |
| Participant flow | Screened, randomised, completed, withdrawn counts | Mirrors a CONSORT flow diagram |
| Baseline characteristics | Demographics form | Reported by arm in the results section |
| Adverse events | AE log, serious and non-serious | Results tables summarise events by arm |
Set up the study, enrol sample participants and export clean datasets in the free sandbox. No credit card.
In Capture
Capture does not submit records to ClinicalTrials.gov for you; the registry entry is made by the responsible party on the registry's own system. What Capture gives you is the clean underlying data: participant status by site, adverse events as repeating rows with an audit trail, and CSV or Excel exports with an automatic data dictionary, plus SDTM datasets as SAS XPT with Define-XML.
| SUBJ | ECGPERF_CODE | ECGPERF_LABEL |
|---|---|---|
| 01-001 | Y | Yes |
| 01-002 | ND | Not done |
A free public registry and results database of clinical studies, maintained by the US National Library of Medicine at the National Institutes of Health.
The unique identifier assigned to each ClinicalTrials.gov record: the letters NCT followed by eight digits. It is quoted in papers and regulatory documents.
No. Registration makes the trial publicly visible. Approval comes from ethics committees and, where needed, regulators.
Not all. US law covers defined "applicable clinical trials", and journals, funders or other regulators may add their own requirements. Check the current rules for your trial.
For trials covered by the US rule, results are generally due within one year of the primary completion date, with provisions for delays and extensions. Confirm against the current regulation.
Sometimes. ICMJE accepts registration in certain recognised registries. Check what your funder, ethics committee and target journal require.
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