Shared medical decision making is a process by which patients and providers consider outcome probabilities and patient preferences and reach a health care decision based on mutual agreement. Shared decision making is best used for problems involving medical uncertainty. During the process the provider-patient dyad considers treatment options and consequences and explores the fit of expected benefits and consequences of treatment with patient preferences for various outcomes. This paper reviews the literature on shared medical decision making. Several questions are considered. Although several studies suggest that patients do not want to be involved in decision making, these studies typically fail to separate decisions about technical aspects of treatment from preferences for outcomes. There is considerable evidence that patients want to be consulted about the impact of treatment. Studies on the acceptability of shared decision making for physicians have produced inconsistent results. Shared decision making is more acceptable to younger and better-educated patients. It remains unclear whether shared decision making requires expensive video presentations or whether the same results can be obtained with simpler methods, such as the decision board. We conclude that shared medical decision making is an important development in health care. More research is necessary to identify the effects of shared decision making on patient satisfaction and health outcomes. Further, more research is necessary in order to evaluate the most effective methods for engaging patients in decisions about their own health care.