We recently experienced a 43-year-old man with a large, multiloculated, cystic tumor that appeared on the pelvis. The tumor was composed of glands and cysts lined by prostatic-type epithelium and attached microscopically to the prostate by a pedicle. The prostatic nature of the lesions was confirmed by immunohistochemical staining of epithelium for prostate specific antigen (PSA). Our review of literature disclosed nine similar cases in men of various ages, originated from the prostate and grew to massive proportions. The lesions in these reported cases did not invade contiguous structures but they can adhere to viscera in their proximity. The multilocular prostatic cystadenoma is a pathologically benign entity, and they can be definitively treated by a carefully planned complete surgical excision. This lesion should be included in the differential diagnosis of retroperitoneal cystic tumors in man. We report a rare case of multilocular prostatic cystadenoma that did not invade adjacent organs and showed no evidence of recurrence after complete surgical excision.