Research on the use and effectiveness of mental health services conducted across a wide variety of settings, under new and diverse state-based legal statutes, and requiring the linking of a variety of existing and proposed data sources raises a number of ethical considerations. These new conditions are reviewed in the context of federal regulations for the protection of human subjects and, in particular, informed consent. Illustrations, suggestions, and resources are offered from recent experiences in a longitudinal, multisource study of the impact of a hospital closing on individual consumers, families, workers, and system costs. (Authors)