Objectives: To examine medical and nonmedical users of prescription opioids, central nervous system depressants, and stimulants taken individually and in combination. Participants: Undergraduates at an urban mid-Atlantic university with 12,000 students. Methods: A questionnaire administered in classes provided 413 responses, with a usable response rate of 94%. Results: Nonmedical users obtained prescription drugs from friends and took them with friends. More nonmedical users than medical users took combinations of drugs. Nonmedical users did not show strong preferences for particular drugs. Nonmedical users compared to medical users who took only 1 drug were more likely to take stimulants and less likely to take opioids. Conclusions: The nonmedical use of prescription drugs by college students is a social activity that involves sharing drugs and taking combinations of drugs with friends. Discouraging nonmedical use must focus on the dangers of combining drugs, sharing drugs, and using social gatherings to consume drugs. (Contains 3 tables.)