A case of hemangiopericytoma in the pelvic retroperitoneum is reported. The patient, a 45-year-old man, visited us with a complaint of sudden urinary retention. Intravenous pyelogram and computerized tomographic scan revealed a large pelvic mass displacing the bladder to the left superiorly. Laparotomy was performed, and biopsy showed the mass to be a malignant hemangiopericytoma. He underwent a surgical excision after receiving irradiation to the true pelvis and embolization of right internal iliac. He developed multiple pulmonary and liver metastases and died 2 years after surgery. Thirty cases of retroperitoneal hemangiopericytoma reported in Japan are reviewed.