Few studies have addressed the variables that affect physicians' practice behavior in treating alcoholism. In the study reported here, the authors hypothesized that alcohol-related training and experience would influence practice behavior more significantly than attitudes or knowledge. In order to assess the most important predictors of practice behavior, the authors conducted a survey of 163 junior and senior medical residents at five training hospitals affiliated with Harvard Medical School. Of these residents, 123 responded (75 percent). Negative attitudes toward alcoholics and knowledge of alcoholism were not significantly related to the residents' estimates of the prevalence of alcoholism among their patients, to their rate of treating alcoholic patients, or to their rate of referring patients for alcoholism therapy. There was a significant relationship between having supervised clinical experience in alcoholism and these three behaviors. These results are consistent with the authors' hypothesis that changing physicians' practice in treating alcoholics may be best achieved by providing relevant clinical experience in alcoholism.