ABSTRACT: In this study, the authors identify differences in barriers to exercise among high school students (n = 236) according to gender and self-reported levels of physical activity. Major barriers to exercise were “time constraints,” “unsuitable weather,” “school and schoolwork,” and “lack of interest or desire.” Univariate ANOVAs revealed adolescent males had significantly higher scores than females for “use of alcohol and drugs” and “having a girlfriend,” while “time constraints” was a significantly greater barrier to exercise among females. Discriminant analyses indicated the barriers of “having a girlfriend” and “use of alcohol and drugs” also distinguished highly active males from highly active females. Results are discussed and suggestions are offered concerning how to reduce perceived barriers to exercise among adolescents. (J Sch Health 1989;59(4):153–155)