The topic of psychoactive drugs is one of inherent interest to college students. We used this insight to design and implement a multidisciplinary undergraduate course with psychoactive drugs as the central theme. The Medical Science of Psychoactive Drugs examines the biological mechanisms underlying all major effects of psychoactive drugs, including the effects on the brain and other organs and tissues. Physiological principles, molecular mechanisms, and genetic factors involved in drug-induced therapeutic and adverse effects are emphasized. The course is open to undergraduate students at all levels and carries no prerequisites, and enrollment is limited to [similar to] 50 students. Major teaching modes include lecture, short homework papers on topics related to the previous class meeting, small-group discussions at several points during each class, and whole class discussions. Because of the diversity of students' knowledge of basic science, we employ a variety of methods designed to help students grasp the necessary scientific concepts. Our methods are intended to be inquiry based and highly interactive. Our goals are 1) to foster the development of an organized knowledge base about psychoactive drugs that will have practical applicability in the daily lives of the students; 2) to promote the rational application of this knowledge in thinking about current medical, social, legal, and ethical issues involving psychoactive drugs; and 3) to cultivate science literacy, critical thinking, and communication skills among students. (Contains 3 tables and 1 figure.)