Thirteen patients were operated on for acute obstruction of the main renal artery (17 kidneys at risk). The operation took place 18 hours to 36 days after the onset of the obstruction. Three nephrectomies were necessary, revascularization was possible in all other cases. Postoperative mortality rate was 15,4%, kidney salvage rate was 64,5%. The function of preserved kidneys was constantly satisfactory. This surgical experience has led us to the following conclusions: acute obstruction of a main renal artery does not necessarily cause renal infarction; viability of the kidney can be maintained over long periods of time thanks to the collateral circulation; neither a functional arrest of the kidney, nor the duration of obstruction must be regarded as signs of renal infarction; no investigation can provide information as to the exact condition of the kidney before surgery; apart from critically ill patients or segmental renal obstruction, treatment should be surgical, irrespective of the time elapsed since onset.