Forty-three children with normal urograms and with kidneys of normal size regarding length, area and parenchymal thickness were examined using a water-delay computerized ultrasonographic equipment. Renal parenchymal volumes were calculated and related to body weight. The correlation coefficient was 0.92. The renal parenchymal volume of the left kidney was significantly larger than that of the right kidney (p less than 0.001). For practical purposes they should, however, be assumed to be of equal size, 2.0 +/- 0.3 cm3/kg body weight.