In a child born with traumatism to a diabetic mother, an acute thrombosis of the left renal vein occurred. An arteriography performed at the acute stage, established the diagnosis. The newborn received urokinase and heparin administered through an arterial catheterism. An arteriography, repeated at the 3rd day, showed an improvement in the vascularization of the kidney, which returned to normal functions. The radiological symptons of renal vein thrombosis are reviewed including the arteriography which is never used for the diagnosis in newborns. The interest of the use of urokinase and its efficiency in this disorder are discussed. This therapy harmless and efficient seems of interest. Such a therapy has to be tried because of the failure of isolated heparin-therapy and of the sequellae which may be observed after spontaneous recovery or after anticoagulant treatment.