Despite notions that patients are now playing a more proactive role in directing their own health care, our study of breast cancer patients considering adjuvant therapy indicates that, at least for a life-threatening illness, patients still rely heavily on their physicians to make treatment decisions. Out of 100 patients, 80.0% accepted their physician's primary treatment recommendation. Using behavioral decision-making theory we examined why some patients chose to disregard the physician's treatment recommendation despite its importance within the decision-making process. The discriminant function analysis performed to examine the factors influencing acceptance or rejection of a physician's treatment recommendation identified two sets of factors. Factors related to the amount and specificity of information about treatments conveyed to the patients, and the strength of the treatment recommendation itself. Patients who did not accept their physician's treatment recommendation were told in more specific terms what the benefits of treatment would be; they also rated side effects of treatment to be more probable and more severe than patients who did concur with the physician's treatment recommendation. These patients also rated their physicians' treatment recommendations as less strong than other physicians'. Nonacceptor patients were also better educated and were more likely to be risk takers. This study supports the findings of other studies that patients want more specific disease and treatment information, but suggests that the provision of this information might lead to therapy decisions which diverge from physicians' recommendations.