This study examines the personal and attitudinal variables that are associated with helping behavior in a hypothetical general practice setting. We explored the effect of an antistigma seminar during a psychiatric clerkship on medical students’ attitudes toward the mentally ill. We randomly assigned three rotations of students (81 students) to receive the seminar and three rotations (85 students) as controls. The students expressed views about patients with schizophrenia or depressive disorder portrayed in video vignettes. How dangerous the students perceived target individuals to be was the major determinant of helping behavior. The students’ gender, religious affiliation, affective reaction, skill assessment, and controllability attribution were less consistent in predicting behavior. Exposure to the seminar and clerkship experience significantly improved attitudes, but attributes of responsibility and readiness to provide medical care for psychiatric patients were the most resistant to change. We identified certain issues that should be highlighted in future antistigma programs.