Forced expiratory vital capacity (VC), forced expired volume during the 1st second (FEV1) and peak expiratory flow (PEF) were measured preoperatively and during the first four postoperative days in 44 patients undergoing cholecystectomy. 18 patients had a muscle splitting incision (M.S.), with no transection of the abdominal muscles; 15 patients had a subcostal incision with transection of the rectus muscle; 11 patients had a midline incision with transection of linea alba. Postoperatively, VC and FEV1 were reduced to 75% of the preoperative value with a m.s. incision, and to 40-55% with a subcostal or midline incision PEF was reduced to 65% of the initial value with a m.s. incision and to 50% with the other incisions. Almost every second patient with a m.s. incision had returned to the initial VC and PEF within four days, whereas only one did so with a subcostal or mid-line incision. In conclusion, the m.s. incision reduces postoperative ventilation efficiency less than other incisions. Its use may reduce postoperative pulmonary complications and shorten the hospital stay.