Seventeen patients admitted to the hospital to undergo elective upper abdominal surgery were randomly assigned to one of the two treatment groups: intermittent positive pressure breathing or physiotherapy. Postoperative pulmonary care in the two groups differed only with regard to administration of intermittent positive pressure breathing and chest physical therapy. Prospective evaluation included clinical examination, whole body plethysmography and determination of arterial blood gases preoperatively and on the 3rd postoperative day. Preoperative pulmonary function data were remarkably similar in the two groups. There was no difference in postoperative plethysmographic status in the two groups. Although not statistically significant, the postoperative decrease in paitial arterial oxygen pressure was more pronounced in the physiotherapy group. Neither of the two therapeutic modalities is more effective than the other in preventing postoperative pulmonary complications. Considering the potential hazards, chest physical therapy is clearly the preferred treatment.