Eighty seven patients, undergoing open heart surgery, were tested preoperatively and postoperatively (on the first, the second, the sixth and the eighth postoperative day) with a Vitalograph spirometer on Forced Vital Capacity (FVC), Forced Expiratory Volume at 1 second (FEV1), Forced Expiratory Flow (FEF) and Forced Midexpiratory Flow (FMF). Preoperative values in this patients were surprisingly good compared with the values calculated from the nomograms presented by Kamburoff et al. (1). Nevertheless three high risk groups were found. Postoperative values for each measured parameter were very low especially on the first and second postoperative day. This easy practicable method gives a more objective approach of the restricted pulmonary function of patients undergoing open heart surgery.