The prevalence of adolescent alcohol use has prompted interest in identifying the factors associated with its use. A comprehensive theory that provides a framework for understanding alcohol use is Jessor and Jessor's Problem Behavior Theory (PBT). We adopted PBT in a study of alcohol use among 226 Catholic high school students. PBT explained 38% of the variation in quantity-frequency of alcohol use and 31% of the variation in problem drinking. The three major systems (personality, perceived environment, behavioral) of the theory were about equally predictive of alcohol use.