To assess the prevalence and motives for illicit use of prescription stimulants and alcohol and other drugs (AODs), associated with these motives, the authors distributed a self-administered Web survey TO a random sample of 9,161 undergraduate college students. Of the study participants, 8.1% reported lifetime and 5.4% reported past-year illicit use of prescription stimulants. The most prevalent motives given for illicit use of prescription stimulants were to (1) help with concentration, (2) increase alertness, and (3) provide a high. Although men were more likely than women were to report illicit use of prescription stimulants, the authors found no gender differences in motives. Regardless of motive, illicit use of prescription stimulants was associated with elevated rates of AOD use, and number of motives endorsed and AOD use were positively related. Students appear to be using these prescription drugs non-medically, mainly to enhance performance or get high.