Three cases of acute thrombosis of the renal artery following an abdominal angiography were operated on. In each case a tight stenosis of the renal artery was present. Two different clinical features were observed: when the thrombosis occurs in a solitary kidney, anuria follows immediately the angiography and this is highly suggestive of the diagnosis; when the contralateral kidney functions well, the thrombosis, probably, will not be recognized. Treatment should always be surgical. In two cases emergency surgery resulted in kidney salvage, whereas in the last the diagnosis was overlooked and delayed surgery could not avoid nephrectomy. Viability of the kidney may be ensured by the collateral circulation and this fact justifies surgery in all cases.