Acute elevation of intra-abdominal pressure above 30 mmHg caused oliguria in 11 postoperative patients. Operative re-exploration and decompression in seven patients resulted in immediate diuresis. Four patients who were not re-explored developed renal failure and died. If intra-abdominal pressure rises above 25 mmHg in the early postoperative period and is associated with oliguria and normal blood pressure and cardiac index, the patient should undergo re-exploration and decompression of the abdomen.