The influence of Italian physicians' attitudes, beliefs, and personal characteristics on medical decision making is examined in the case of surgical treatment of early breast cancer. Responses to a mail survey of 657 physicians from different specialties were analyzed comparing doctors recommending a radical procedure (9%) to those preferring a conservative procedure for younger patients only (25%), and those considering conservative surgery the treatment of choice regardless of patients' age (66%). The findings suggest that the likelihood of physicians' preferring a conservative procedure is influenced by their specialty and the extent to which they feel that a patient should have a role in the treatment decision more than by differences in the beliefs of treatment outcomes. Only preferences of the small group indicating radical surgery as the sole admissible treatment can be accounted for by ignorance or distrust of results of recent trials. These findings suggest that other than scientific factors guide many doctors in their decision making; they may help to explain why the diffusion of research results into clinical practice is often disappointingly slow.