Renal cystic disease encompasses a complex group of pathologic and clinical entities, with varied yet distinctive sonographic features. An accurate assessment of the fetal genitourinary tract and the amniotic fluid volume by sonography can lead to a specific prenatal diagnosis in most cases. This article emphasizes the usefulness of sonographic-pathologic correlation in understanding renal cystic disease. The entities discussed are infantile polycystic kidney disease (Osathanondh and Potter type I), multi-cystic renal dysplasia (type II), adult polycystic kidney disease (type III) and renal cystic dysplasia associated with obstructive uropathy (type IV). Sonograms of six correctly diagnosed cases between November 1982 and November 1984 were retrospectively reviewed and correlated with their pathologic findings. The differential diagnosis and possible pitfalls are discussed. In addition, the impact on perinatal management and the role of genetic counselling will be emphasized.