Bilateral renal agenesis is a lethal congenital anomaly. A reliable prenatal diagnosis is extremely important, since it may offer options for pregnancy termination or may change obstetric management in the third trimester. This study examined the accuracy of ultrasound in making an antenatal diagnosis of bilateral renal agenesis in three different populations: (1) patients with a family history of bilateral renal agenesis, (2) patients diagnosed during the course of a routine scan, and (3) patients referred because of a previous suspicious ultrasound examination in a level I ultrasound facility. In group A there were three true positive, 13 true negative, no false negative, and no false positive diagnoses. In group B there were three true positive and no false positive diagnoses. In group C there were 12 true positive, 17 true negative, one false negative, and no false positive diagnoses. The value and potential pitfall of the different diagnostic criteria are discussed. We conclude that ultrasound is a valuable tool in the detection of intrauterine renal failure, although there are limitations to a specific diagnosis of bilateral renal agenesis.