About 50% of the cases with Castleman disease firstly described by Castleman in 1956 occur in the thoracic cavity. The pelvic cavity is a rare location affected by the disease; there are only 7 reports. Herein, a case of Castleman disease of the pelvic cavity is reported. A 41-year-old man complaining of microscopic hematuria consulted us. Drip intravenous pyelography and computerized tomography showed a solitary mass at the pelvic retroperitoneum. Abnormal laboratory findings were as follows; glucose tolerance test (GTT), erythrocyte sedimentation rate, alpha 2-globulin level, CRP titer and hematuria. With the diagnosis of a pelvic retroperitoneal tumor, pelvic exploration was performed. The resected tumor was encapsulated, elastic hard and 4x3x2 cm in size. The cut surface was homogeneously granular and yellowish white in color. Histological diagnosis was the plasma cell type of Castleman disease. Within three weeks after the operation, laboratory abnormalities diminished except for GTT and microscopic hematuria. The patient is free from the disease with no signs of recurrence for 2 years postoperatively.