The purpose of this paper was to describe the development of a comprehensive, stage-based model for the prevention of drug use titled the multi-component motivational stages (McMOS) model. The McMOS model is proposed as a multielement, integrative theoretical framework for the development of prevention strategies and content which are matched to the developmental stages of drug use among youth, based on previous work by Prochaska and DiClemente. The major components of the McMOS drug prevention model include: (1) a stage-based framework which permits the matching of prevention strategies and messages to youths' stage of development in the change process; (2) the delineation of a continuum of stages ranging from the acquisition of drug use through the successful modification of drug use; (3) a two-level prevention schema for targeting a broader range of youth for intervention, including those regularly using drugs as well as those not yet regularly using drugs; (4) a drug specific emphasis for proposing prevention strategies targeting the most prevalently used drugs, based on epidemiologic research; (5) the delineation of major theoretical constructs influencing the movement of youth through the stages, based on three prominent behavioral theories; and (6) a framework for selecting a range of prevention delivery modes for youth at all stages and levels of behavioral change.