We report a case of infectious cysts of Müllerian duct. A 48-year-old male patient was referred to our department complaining of terminal miction pain on July 19, 1985. The excretory urogram showed right lateral displacement of bladder and pelvic CT-scan demonstrated a large mass containing multiple cysts. A total of 5 percutaneous punctures was performed, but without success. The cysts were removed completely on November 26, 1985. A large volume of pus subsequently yielded a pure culture of Serratia marcescens and multilobular cysts were observed in the incised tumor. Wound healing was delayed because of severe infection. We discussed the difficulty of the management for infectious cysts of the Müllerian duct.