Randomized clinical trials: issues for researchers.

The clinical trial is a randomized prospective study of human subjects in which the effectiveness of an intervention is compared against a control. Such a trial is considered to be a critical test of an innovative therapy. Trials require careful design and planning to be scientifically valid and clinically pertinent. In this review the clinical trial and its role in research are defined, and major ethical, methodological, and feasibility issues associated with trial design and organization are described.