Incentive spirometry, as a method for preventing postoperative atelectasis, was compared with intermittent positive-pressure breathing (IPPB) and resistance breathing in 126 patients undergoing upper-abdominal surgery, most of whom had cholecystectomy. There was no statistically significant difference in the incidence of atelectasis among the three groups, who were matched for age, sex, smoking history, previous respiratory disease, and duration of surgery. There was a significantly higher incidence of atelectasis in patients over the age of 50 years (P = 0.004) than in younger subjects, where the incidence was not different among the three groups. Incentive spirometric therapy, as used in this study, offered no advantage over the other methods of treatment.