The purpose of this study was to develop and evaluate an educational intervention designed to modify the stigma held by first-year medical students towards obese patients. The intervention, composed of video, audio and written components, was based on Petty and Cacioppo's elaboration likelihood model. Prior to the course, the medical students held largely accurate beliefs about the causes of obesity, but they still maintained negative stereotypes of the obese as lazy and lacking in self-control. Analysis of students' attitudes toward obese patients five weeks and one year after the course indicates that the intervention was effective. At the five-week assessment, students in the intervention group differed from students in the control group on six of eight measures of attitudes toward the obese. One year after the course, the intervention group was significantly more likely to rate genetic factors as important in obesity and less likely to blame the obese for their condition.