Objective: The authors compared the prevalence and pattern of substance use in undergraduate student athletes and nonathletes from 2005-2006. Participants: Authors collected data from male (n = 418) and female (n = 475) student athletes and nonathletes from 2005-2006. Methods: The authors administered self-report questionnaires to assess prevalence, quantity, and frequency of alcohol and drug use, and to determine patterns of student athletes' alcohol and drug use during their athletic season versus out of season. Results: Male student athletes were at high risk for heavy drinking and performance-enhancing drug use. Considerable in-season versus out-of-season substance use fluctuations were identified in male and female student athletes. Conclusions: Additional, and possibly alternative, factors are involved in a student athlete's decision-making process regarding drug and alcohol use, which suggests that the development of prevention programs that are specifically designed to meet the unique needs of the college student athlete may be beneficial. (Contains 4 tables.)