Purpose: An increasingly important task for all disciplines involved in aging research is to identify and prioritize areas for investigation. This article reports the results of a national Delphi study on setting research priorities for gerontological social work. Design and Methods: Delphi methodology, a structured process for eliciting and correlating informed opinions from a panel of experts on a specific topic, was used. A national expert panel of 46 gerontological social workers completed three successive Web-based questionnaires with controlled feedback to delimit a set of high-priority research topics. Results: There were 49 independent research topics identified, 16 of which attained high or highest priority and high or moderate consensus ratings. The top-priority topic was developing and testing psychosocial interventions across specific populations and conditions. Three additional topics on intervention research achieved similar ratings, as did all four topics on services research. Implications: The research priorities identified by expert panelists in this study represent critical knowledge needs for the social work profession in aging, and they overlap and complement the current research agendas of the National Research Council and the National Institute on Aging. They are thus expected to help guide the development and prioritization of social work and interdisciplinary research to improve practice and policies affecting older adults and their families.