Hemangiopericytoma (HPC) of the viscera is very rare and only six of these tumors arising in the urinary bladder have been previously reported. The differentiation of HPC from other neoplasms with prominent vascular pattern may be a diagnostic problem. The difficulty is further enhanced by the lack of distinctive immunohistochemical features of this tumor. Here is presented a case of benign HPC occurring in the right lateral wall of the bladder of a 37-year-old woman. The mass is completely transurethrally resected. Histologically, the tumor is characterized by a monomorphic population of polygonal or spindle-shaped cells packed around branching vascular channels, with "staghorn" configuration. There are no foci of necrosis or hemorrhage. The mitotic count is 2 per 10 HPF. Immunohistochemically, the tumor cells react with anti-bodies against Vimentin. Cytokeratin, Actin HHF35, S-100, CD 34, Factor VIII-related antigen are not expressed within the lesion. Ultrastructurally, the tumor cells surround endothelium-lined vascular channels. There are pinocytotic vesicles on the cell borders. The cells are separated from one another by deposits of basal lamina-like material and collagen. On the basis of clinical, histological, immunohistochemical and ultrastructural observations, we believe that the case reported is a primary benign HPC of the bladder. There is no evidence of recurrence or metastasis 32 months later.