The American population aged 65 years and older is growing rapidly, creating an increased demand for social workers. Reimbursement structures of Medicare and Medicaid present significant barriers for aging individuals seeking social work services as well as social workers wanting to provide services to the elderly. To build a case for the modification of these reimbursement structures, a review of studies of social work services in aging was conducted to (a) make explicit the current knowledge of the efficacy and cost-effectiveness of these services, (b) identify current gaps in knowledge, (c) promote a research agenda to address the gaps, and (e) assure that the knowledge identified addresses payers' needs to understand the value of social work services in aging. The results indicate that social work interventions can have a positive impact on the health care costs, the use of health care services, and the quality of life of older Americans. (Contains 1 table.)