The role of ultrasound in detecting fetal anomalies in general and genitourinary tract anomalies in particular has undergone, and continues to undergo, remarkable changes. The diagnostic process began with a focus on the structural nature of anomalies and now has moved forward to include a detailed assessment of the functional nature and sequelae of these lesions. Concurrent with this shift in diagnostic emphasis has been the development of the role of ultrasonography in guiding invasive diagnostic procedures, such as percutaneous fetal blood sampling and fetal urine aspiration, and in guiding therapeutic procedures, such as chronic in utero vesicoamniotic shunt placement. These changes are occurring against a background of the role of ultrasound in assessing pathophysiology of the anomaly and assignment of prognosis, two decisions that profoundly influence pregnancy management. The challenge for the perinatal ultrasonographer is now not only to recognize the lesion, but also to institute the further investigative steps upon which a rational management plan may be based. As illustrated in this brief review of the more common genitourinary tract anomalies, the range of outcome and the pathophysiologic progression of the disease are both wide and complex. Continued improvements in ultrasound technologies and application hold the key to the ultimate reduction in the clinical significance of these common fetal diseases.