Congenital prepubic sinus (CPS) is a rare congenital anomaly which is associated with discharge from an opening overlying the pubis symphysis. Various names including congenital prepubic sinus, subpubic fistula, prepubic dermoid sinus, and suprapubic dermoid sinus, were us ed to identify these lesions. The etiology of CPS is still controversial. There are 2 theories that have been proposed, including an anomalous anterior abdominal wall closure or variant of dorsal urethral duplica- tion.1-4 To explore the etiology, we performed immuno- histochemical study with 3 cytokeratin antibodies that are known to be specific for differentiation between transitional and squamous epithelium.