Existing empirical literature on the prolonged or cumulative consequences of exposure to the stresses of caregiving is reviewed. Specific goals are to identify psychiatric and physical morbidity effects, report the magnitude of those effects, evaluate research and analytic methods used to assess morbidity, and make recommendations for future research. Overall, the literature indicates increases in self-report psychiatric symptomatology and increases in psychiatric illness among most caregivers when compared to population norms or appropriate control groups. However, there is little information on the population prevalence or incidence of clinically significant psychiatric conditions attributable to caregiving. Studies of physical health effects as assessed by self-report, health care utilization, and immune function are less conclusive but, nevertheless, suggest increased vulnerability to physical illness among caregivers. We conclude with a discussion of why morbidity effects are difficult to obtain in caregiver studies and with recommendations for future research.