The purpose of this study was to determine whether the use of intermittent positive pressure breathing during inspiration (IPPB[I]) combined with administration of nebulized isoproterenol (Isuprel) would reduce the incidence of postoperative pulmonary complications. There were 160 patients in the control group and 42 in the group receiving IPPB(I) with isoproterenol. The treated group contained more patients of more than 60 years of age and more with maximum breathing capacities of less than 60% of that predicted; otherwise, the two groups were similar. Significant postoperative pulmonary complications were experienced by 19.5% of the control group and 2.5% of the treated group. The incidence of postoperative pulmonary complications in the control group was 2.5 times as great for those patients who had maximum breathing capacities of less than 60% of that predicted than for those in the same group whose maximum breathing capacities were greater than 60% of that predicted.