Urgent nephrectomy was once considered standard therapy for renal venous thrombosis, but recently nonoperative therapy has been advised. To examine this trend more closely, we reviewed 46 cases of renal venous thrombosis seen at the Children's Hospital of Pittsburgh (Pa) over the last 32 years. Earlier, diagnosis was frequently supported by intravenous pyelography, which was 79% accurate. More recently, sonography confirmed the diagnosis with 92% accuracy. Of 21 patients diagnosed during life, 4 were treated operatively and 3 survived. Of 17 patients treated nonoperatively, 14 (82%) survived, including 5 with bilateral disease. Since 1978, of the 10 patients treated nonoperatively, 9 have survived with no long-term morbidity. Our experience confirms that early diagnosis with sonography followed by supportive nonoperative therapy offers the best chance for success in patients with renal venous thrombosis.