The NIH defines a clinical trial as a prospective biomedical or behavioral research study of human subjects that is designed to answer specific questions about biomedical or behavioral interventions (drugs, nutritional supplements, surgical intervention, or devices). Clinical trials are used to determine whether new biomedical or behavioral interventions are safe, efficacious, and effective. Behavioral clinical trials involving an intervention to modify behavior (diet, physical activity, cognitive therapy, etc.) fit this definition of a clinical trial.

An overview of clinical trials