Two cases of congenital saccular diverticulum of the penile urethra occurred. In both, lower obstruction caused varying degrees of hydronephrosis and uremia. In the first case, renal damage was so extensive by the time of operation at the age of 13 days that the infant died shortly afterwards (autopsy revealed typical changes in the urethra as well as in the kidneys). In the second case renal damage progressed more slowly and was discovered when the patient was 18 years old; surgery was subsequently performed. The roentgenological findings in both cases are presented. This malformation has been reported to be of embryological origin, a finding confirmed by our pathological studies. The importance of early diagnosis and surgical treatment is stressed.