Typical research models of social support are overly simple on two grounds. First, they treat social support as exogenous to the model. That is, models incorporate the effects of social support on stressors and on psychological distress, but typically ignore the influences of stressors, psychological distress, personal characteristics of recipients, and environmental constraints on support. Second, the models typically consider only positive consequences of social interactions, although these interactions may also have negative consequences. Further, actions that are perceived as helpful by the donor, the recipient, or both can have harmful effects if they do not fit individual circumstances. Five dimensions of fit between the characteristics of the recipient and those of the supportive act are proposed: amount, timing, source, structure, and function. Implications for research and intervention are discussed.