In a premature infant bilateral renal venous thrombosis and associated thrombosis of the inferior vena cava were diagnosed at the age of 6 weeks, using a 2-dimensional ultrasound sector scanner with integrated pulsed doppler ultrasound of the renal vessels. In contrast to 30 healthy children, who showed continuous forward flow in the renal arteries throughout systole and diastole, diastolic flow was decreased or even retrograde in renal venous thrombosis (RVT) according to the severity of thrombosis. Doppler recordings in renal veins normally showed continuous retrograde flow patterns, whereas in RVT venous flow was decreased or absent. Pulsed doppler ultrasound is a useful and noninvasive method for recording renal flow patterns, especially in renovascular disease.