Six patients who had neonatal renal vein thrombosis underwent re-evaluation of renal function 21 months to 12 years after initial diagnosis. Plasma creatinine clearances were normal in all patients as was urinary concentrating ability and urinalysis. Five patients had elevated systolic and diastolic blood pressures. However plasma renin activities were normal. Intravenous pyelography and renal scintigraphy revealed morphologic abnormalities in four patients. This study emphasizes that after apparent full recovery from neonatal renal vein thrombosis, arterial hypertension may persist and warrants careful long-term follow-up.