A 54-year-old man was evaluated for symptoms of bladder outlet obstruction. Evaluation revealed a 10 by 9.8-cm tumor composed of bland, fibroblastic, poorly cellular material adjacent to the prostate. Administration of a course of antiestrogen (tamoxifen) and a nonsteroidal anti-inflammatory agent (sulindac) resulted in prompt relief of symptoms and a slow decrease in the size of the tumor as measured by computed tomography. After 54 months of therapy, the tumor was undetectable clinically and dramatically reduced in size as seen on computed tomography. Data on the natural history of desmoid tumors and the efficacy of various therapeutic strategies are reviewed.