The effect of epidural anaesthesia of limited duration on postoperative protein breakdown was studied in elderly patients undergoing hip arthroplasty. Two groups of six patients each were studied. One group with halothane (C) and one with an epidural block, T8-S4, (E) as part of their general anaesthetic for surgery. The urinary excretion of urea nitrogen and 3-methylhistidine (3-MeH), an indicator of muscle protein breakdown, increased significantly in both groups after surgery, by the same amount (P less than 0.05). The total concentration of plasma and muscle aminoacids decreased after surgery in both groups. Muscle glutamine was decreased by 50% after surgery on the fourth postoperative day in both groups (P less than 0.05). Therefore epidural anaesthesia, limited to the period of surgery, did not attenuate the loss of body proteins which occurred during the postoperative period.