Hospital social workers strive to define their professional domain to avoid blurring their roles with those of other health care professionals. Hospital social workers are concerned with gaining and retaining recognition by patients, families, and colleagues of their distinct professional contribution. This article reviews the evolution of social workers' roles and functions in hospitals and reflects on the frequently noted discrepancy between self-ascribed roles and those conceded to social workers by other health care professionals. Issues of collaboration in the context of interdisciplinary activity are considered, and the impact of overlapping roles on social work practice is assessed. The value and drawbacks of role ambiguity are discussed, and strategies for role clarification and development of a better-defined domain for social workers in hospitals are recommended.