In many medical schools instruction of students in clinical pharmacology remains informal and may be inadequate. To determine the short-term efficacy of a mandatory senior medical year course in clinical pharmacology, we compared examination scores of senior students in the College of Medicine, University of Iowa, either prior to or following the Clinical Pharmacology and Therapeutics Lecture Series. A significantly higher (P less than .001) mean score was demonstrated by students taking the examination following the course (75 +/- 4% correct) versus those taking the examination prior to the course (55 +/- 4% correct). To determine student acceptance, postcourse questionnaires were completed. Students surveyed immediately postcourse and alumni surveyed up to four years after graduation highly recommended the course and favored retaining it as a mandatory part of the fourth-year curriculum. This study confirms the efficacy and acceptance of senior medical courses in therapeutics and suggests an effective role for clinical pharmacologists in their design and execution.