Since its introduction into medicine 15 years ago, decision analysis has been applied to difficult clinical problems. Several important advances have made the process more practical and acceptable: computer programs that eliminate the need for burdensome calculations, improved techniques for designing analytic models, the ability to carry out sensitivity analyses over several dimensions simultaneously, and the elaboration of clinically relevant measures of utility. Using these techniques, analysts have addressed many important clinical issues including screening for and prevention of disease, tradeoffs among tests and treatments, and the interpretation of clinical data under conditions of uncertainty. Problems with the approach remain and applications have not been extensive, but decision analysis is evolving as a powerful clinical tool and gradually is gaining acceptance in medical practice.