This study reports on a survey of medical and nonmedical prescription drug use by 3639 students at a large public university. Medical use of sleeping medication, narcotics, stimulants, or sedative/anxiety medications were reported by most respondents, and 1 in 5 reported nonmedical use of at least 1 class of these drugs. The nonmedical use of prescription drugs was associated with a 5- to 6-fold greater risk of having a positive screen for drug abuse compared with nonusers. In contrast, medical use of these drugs was not associated with an increased risk of drug abuse. The appropriate diagnosis, treatment, and therapeutic monitoring of students who are receiving abusable prescription medications is crucial to help prevent the abuse of these medications.