We present a case of a muellerian duct cyst in a 55 year-old man. A cystic lesion was incidentally found between the prostate and the bladder on transabdominal ultrasound examination. Computerized tomography revealed a low density area homogeneous and round with a clear margin. Both urethrocystgram and vesiculogram demonstrated no cystic lesion. On diagnosis of muellerian duct cyst percutaneous needle aspiration was performed under ultrasound control. The aspirated fluid was yellow, clear and negative for cytology. Microscopically no spermatozoa were found in it. Minocycline (100 mg) was injected into the cyst. No recurrence has occurred since the operation. The literature of the cyst was briefly reviewed.