Leiomyosarcoma of the urinary bladder is rare and therefore unfamiliar to most urologists and pathologists. Here we present the case of a 78-year-old male with leiomyosarcoma of the urinary bladder. The clinicopathologic and immuno-chemical features are reported. A review of the literature and an outline of this tumor are presented. This report also discusses the immunochemical methods used in diagnosis, the criterion to distinguish leiomyosarcoma from leiomyoma of the urinary bladder, and treatment of disease.