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Who Can Participate in Clinical Trials?

Each clinical trial defines who is eligible to take part in the study. Each trial must include only people who fit the patient traits for that study (the eligibility criteria). For more information about eligibility criteria, go to "How Do Clinical Trials Work?"

Some trials enroll people who have a specific disease or condition. Others enroll healthy people to test new approaches to prevention, diagnosis, or screening.

In the past, clinical trial participants often were White men. Researchers assumed that trial results were valid for other populations as well.

Researchers now realize that women and people in different ethnic groups sometimes respond differently than White men to the same medical approach. As a result, the National Institutes of Health and the National Heart, Lung, and Blood Institute (NHLBI) are committed to sponsoring clinical trials that include women and that are ethnically diverse.

Children also need clinical trials that focus on them, as medical treatments and approaches often differ for children. For example, children may need lower doses of certain medicines or smaller medical devices. Their stage of development also can affect how safe a treatment is or how well it works.

Children (aged 18 and younger) get special protection as research subjects. Almost always, parents must give legal consent for their child to take part in a clinical trial.

When researchers think that a trial's potential risks are greater than minimal, both parents must give permission for their child to enroll. Also, children aged 7 and older often must agree (assent) to take part in clinical trials.

Clinical trials for children have the same scientific safeguards as clinical trials for adults. For more information, go to "How Do Clinical Trials Protect Participants?"

For more information about clinical trials for children, go to the NHLBI's Children and Clinical Studies Web page.

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Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for Clinical Trials, visit

August 03, 2012 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.