This paper addresses the need for a more systematic framework for conceptualizing and evaluating the health-related effects of support. A conceptual model of stress, support, and functioning is presented which clarifies the direct, interactive, and indirect effects of social support. Several paths representing relationships among life stressors, support, and functioning are presented, including: (1) the adverse effect of stressors on functioning; (2) the direct effect of support on functioning, not contingent on stress levels; (3) the interactive effect of support as a conditioner of the stress-functioning relationship; (4) the indirect effects of support on the occurrence and appraisal of stressful life events; and (5) the effect of stress on influencing the availability of support. Each of these relationships is illustrated with current research results, that suggest mixed evidence for direct and interactive effects, while noting that indirect effects have received little attention. The implications of concepts of support for prevention efforts are also discussed along with the need to consider the varied effects of support in designing prevention programs. (Author/NRB)