Twenty male patients undergoing elective abdominal surgery were studied on one control day pre-operatively and for the first 4 days postoperatively at an environmental temperature of either 20 degrees C or 28 degrees C. Glucose, insulin, growth hormone and urinary catecholamine levels all rose significantly on the first postoperative day returning to within normal limits by day 4. Urine nitrogen excretion also increased significantly postoperatively in both groups. Environmental temperature did not influence these responses. Concentrations of C-reactive protein and a1-antichymotrypsin increased significantly on the first postoperative day and were returning to normal by day 4 while concentrations of haptoglobin, a1-antitrypsin and a1-acid glycoprotein, which also showed a significant increase, remained elevated at the end of the study. Concentrations of albumin, transferrin, a2-macroglobulin, prealbumin and retinol binding protein all decreased significantly following operation. Elevated environmental temperature did not affect the protein response to surgery. Urine cortisol and 17-hydroxycorticosteroid excretion rose significantly postoperatively and remained elevated throughout the study. Patients nursed at 28 degrees C showed significantly lower postoperative excretion of both hormones than patients nursed at 20 degrees C.