Two patients, 1 adult and 1 infant, with complete duplication of the penis are described. The adult had a single bladder, a bifid scrotum, a low abdominal wall hernia, separation of the symphysis pubis, bilateral inguinal hernias, rectal prolapse, bilateral vesicoureteral reflux and bilateral staghorn calculi. The infant had duplication of the bladder, hypoplasia of the left kidney, lumbosacral anomalies, a hypoplastic left lower extremity, an imperforate anus, a infraumbilical wall hernia and separation of the symphysis pubis. A survey of the anomalies accompanying the 2 main types of diphallus (shaft and glans, and glans alone)showed that there was a preponderance of anomalies of posterior structures such as colon, bladder and spine in the shaft and glans diphallus, and a higher incidence of isolated exstrophy of the bladder in diphallus of the glans alone. The embryogenic implications of these findings are discussed.