Pre- and postnatal ultrasound (US) findings and clinical course in 19 fetuses (16-40 menstrual weeks) with hyperechoic kidneys (renal echogenicity greater than that of liver) and no other abnormalities detected with US were evaluated to determine whether increased renal parenchymal echogenicity in the fetus indicates renal disease. Four infants (21%) were healthy at birth and had normal postnatal sonograms. Another 10 infants (53%) survived, but abnormalities were found at neonatal US. Postnatal diagnoses in these 10 neonates included unilateral renal dysplasia (n = 3), unilateral multicystic dysplastic kidney and a contralateral hyperechoic kidney (n = 2), hydronephrosis (n = 2), and renal abnormalities of unknown type (n = 3). Five fetuses with either infantile polycystic kidney disease (n = 4) or bilateral multicystic dysplasia (n = 1) did not survive. Oligohydramnios was predictive of a poor prognosis. Hyperechoic renal parenchyma in the fetus was associated with sonographic or functional abnormalities in 15 of 19 cases (79%) and a 74% survival rate.