This chapter outlines the utility of the health action process approach (HAPA), a hybrid social cognition model that aims to describe, explain, and modify health behaviors. The HAPA combines features of stage and continuum social cognition models. The model makes the distinction between motivational and volitional phases involved in the change process. In the motivational phase, outcome expectancies, action self-efficacy, and risk perceptions are constructs that make formation of intentions more likely. In the volitional phase, coping self-efficacy and action and coping planning are important determinants of behavior, with behavioral maintenance determined by recovery self-efficacy and action control. Behavioral intention bridges the motivational and volitional phases, while planning serves to link intentions with behavior. HAPA-based interventions target change in the appropriate components from each phase most likely to move the individual further toward goal attainment. For individuals who are not motivated to change, interventions targeting change in outcome expectancies, action self-efficacy, and, for some behaviors and in some contexts, risk perceptions promote intention formation. For individuals who already hold intentions to change, interventions focusing on changing coping self-efficacy, planning, and action control are most appropriate. Empirical evidence supports the usefulness of the phase-specific approach to changing behavior proposed in the HAPA.