Over a three and a half year period 32 babies were referred with a urinary tract anomaly diagnosed by prenatal ultrasound. This diagnosis was subsequently confirmed in 19 infants by postnatal assessment. Three of 13 infants in whom the original diagnosis was incorrect were subsequently found to have intra-abdominal pathology but no urological anomaly, while the other 10 had lesions in the urinary tract but not those suggested prenatally. Nineteen of the 29 babies with urological abnormalities were clinically normal at birth; 20 underwent surgery. There were three deaths; two from a combination of renal and pulmonary failure secondary to posterior urethral valves, and a third (in an infant who had normal renal function) from diaphragmatic hernia and cardiac anomalies. Prenatal diagnosis was thought to have been of benefit in six patients, of probable benefit in 16, and of no benefit in seven.