Characteristic changes in the pattern of muscle free amino acids are seen on the third day after elective surgery. The time course of the restoration to normal levels in uncomplicated cases has not been established before. Seven metabolically healthy patients undergoing cholecystectomy were studied. Muscle biopsy specimens and plasma samples were taken before operation and on days 3, 10, 20 and 30 after surgery. The level of total free amino acids in skeletal muscle decreased and the concentrations of branched chain and aromatic amino acids increased on day 3. The original levels were found to be restored on day 10 after surgery. A decrease in glutamine of 38 per cent (P less than 0.001) was seen on day 3, of 20 per cent (P less than 0.05) on day 10 and of 22 per cent (P less than 0.05) on day 30, compared with preoperative values. These results constitute a baseline for future studies in which the impact of nutritional and pharmacological therapies is to be evaluated beyond the immediate postoperative period.