We review the research both for and against patient participation in decision-making and conclude that (a) patients want to be informed of treatment alternatives, (b) they, in general, want to be involved in treatment decisions when more than one treatment alternative exists, and (c) the benefits of participation have not yet been clearly demonstrated in research studies. However, studies that have addressed the latter issue suffer from methodological problems such as small sample sizes and lack of control for potential confounding variables. We conclude that patient participation in decision-making is justified on humane grounds alone and that physicians should endeavor to engage patients in decision-making, albeit at varying degrees, when more than one effective treatment option exists. We propose that methods be developed to evaluate a patient's level of "readiness" to participate in decision-making and that interventions that match the patient's level of readiness be applied to increase participation.