Following cardiac operations, 145 patients were treated with either intermittent positive-pressure breathing (IPPB), blod bottles, or an incentive spirometer in an attempt to alter the incidence of atelectasis. Pulmonary complications occurred in 30% of the patients receiving IPPB, 15% of those using an incentive spirometer, and 8% of those using blow bottles. Gastrointestinal side-effects occurred in 20% of the IPPB group and were rare in other groups. The cost of IPPB is also considerably greater than either incentive spirometry or blow bottles. IPPB is not essential to prevention of atelectasis in postoperative cardiac surgical patients and may be inferior to other methods.