A clinical trial is a research study on human volunteers designed to answer specific health questions. The purpose of a clinical trial is to find out whether a medicine or treatment regimen is safe and effective against a specific condition or disease.

Clinical trials compare the effectiveness of the study medicine or treatment against standard, accepted treatment or a placebo. (A placebo is an inactive substance used to compare results with an active substance). Early (phase I) trials establish the safety, toxicity, and safe dosing ranges of a new treatment.

A clinical trial may be sponsored by a government agency, such as the National Institutes of Health, or a pharmaceutical or biotechnology company. All clinical trials are guided by government regulations. These rules make sure that participants are not likely to be harmed and that they fully understand the risks and benefits of participating.