Autosomal dominant polycystic kidney disease (ADPKD), once thought to be a disease of the adult, is now being reported with increasing frequency in childhood. We report five cases and review eight cases from the literature of ADPKD diagnosed in the fetus or the young infant by sonographic evaluation and a positive family history. Renal enlargement (85%) was the most common and most helpful sonographic finding. Approximately 50% of the patients already had cysts large enough to detect by ultrasound. Increased renal echogenicity was present in nine of 10 cases. Although every case in this review had one parent affected with ADPKD, only five of 13 (38%) were aware of their disease prior to their pregnancy. Renal cystic disease diagnosed in the fetus and young infant should trigger an investigation of the family history and sonographic screening.