In 1021 children, aged several hours to 21 days, sonographic investigations of kidneys and bladders were performed. 1001 children without any urinary tract abnormality were divided into 7 body weight-dependent groups. The kidney volume was correlated to somatometric data including body weight and body length, breadth of thorax, and head circumference. Regression line for the dependence of renal volume on body weight was calculated. The remaining 20 children with urinary tract abnormalities were described separately. During ultrasonic screening examination, bladder or renal disorders found in those 20 children were as follows: mild hydronephrosis in 6 cases, and severe hydronephrosis in 4 cases; of the latter 1 case was caused by ectopic ureterocele, 1 by simple ureterocele, 1 by obstruction of the distal ureter (primary megaureter) and 1 by vesicoureteral bilateral reflux. In 2 cases unilateral multicystic kidneys were found, 2 infants had an ultrasound pattern with hyperechoic medulla, in 4 cases unilateral non-obstructed renal duplication was suspected, and in 2 cases only a single kidney was found.