Clinical Trial
A research study that tests a medical treatment, drug, device, or intervention in human volunteers to determine whether it is safe and effective.
In Detail
A clinical trial is a carefully designed research study conducted with human participants to evaluate the safety, efficacy, and optimal dosing of new medical interventions. These interventions can include drugs, vaccines, medical devices, surgical procedures, behavioral therapies, or diagnostic tools. Clinical trials are the gold standard for generating evidence about whether a new treatment works and is safe enough for widespread use. Every trial follows a protocol, a detailed plan that describes the study's objectives, design, methodology, statistical considerations, and how participants will be protected. In the United States, most clinical trials must be registered on ClinicalTrials.gov, a public database maintained by the National Library of Medicine. Trials progress through distinct phases (Phase 1 through Phase 4), each with a different purpose and scale. Participation is always voluntary, and participants can withdraw at any time. Before any trial begins, it must be reviewed and approved by an Institutional Review Board (IRB) to ensure the rights and welfare of participants are protected. Clinical trials are essential for bringing new treatments from the laboratory to patients, without them, no new drug can receive FDA approval.
Frequently Asked Questions
What does "Clinical Trial" mean in clinical trials?
A research study that tests a medical treatment, drug, device, or intervention in human volunteers to determine whether it is safe and effective.
Why is "clinical trial" important for patients?
Understanding clinical trial helps patients and caregivers navigate clinical trial participation with confidence. It is part of the broader clinical research process that ensures treatments are safe and effective before reaching patients.
Related Terms
Phase 1 Trial
The first stage of testing a new treatment in humans, focused primarily on safety, dosing, and side effects in a small group of volunteers.
Phase 2 Trial
The second stage of testing, which evaluates whether the treatment works for its intended condition and continues to assess safety in a larger group.
Phase 3 Trial
A large-scale study that confirms effectiveness, monitors side effects, and compares the new treatment to existing options, the final step before seeking regulatory approval.
Phase 4 Trial (Post-Marketing)
Studies conducted after a drug has been approved and is on the market, monitoring long-term safety, effectiveness in broader populations, and rare side effects.
Informed Consent
The process by which a potential participant learns the key facts about a clinical trial, including risks, benefits, and alternatives, before deciding whether to enroll.
Institutional Review Board (IRB)
An independent ethics committee that reviews and approves clinical research involving human subjects to ensure participants' rights, safety, and welfare are protected.
this entity is one of the U.S. clinical trials and research registries concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the the NIH ClinicalTrials.gov registry data behind every per-entity page on the site.
In the the NIH ClinicalTrials.gov registry data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.
Source: ClinicalTrials.gov, 2026.