Rats were given 10 or 20 mg of inosine dissolved in 1 ml of 0.9% saline, or a control solution of 1 ml of 0.9% saline, intravenously 10 or 20 min before induction of left renal warm ischaemia for 60 min. Further groups of rats were treated with 20 mg inosine or with saline alone 20 min before longer periods of warm ischaemia of 90 and 120 min duration. All animals had immediate contralateral nephrectomy. In all inosine-treated groups the mean plasma creatinine was lower than in their respective control groups and these differences were statistically highly significant.