Lung volumes after heart-lung transplantation (HLT) were recorded and compared with measurements at the time of assessment for surgery and the predicted values for recipients. The influence of donor lung size and recipients' underlying lung disease was evaluated. All patients underwent HLT between April 1984 and April 1991, and only those 82 who survived for at least 6 mo were studied. Mean total lung capacity (TLC) at preoperative assessment was 112% (SD = 28%) of the value predicted for recipients. One month after HLT, mean TLC was 83% (SD = 15%) of the predicted value but increased to 100% (SD = 15%) after 9 mo. No further change in average TLC occurred for 5 yr subsequently. The mean TLC of patients with emphysema before surgery was 164% (SD = 26%) of the predicted value and fell to the predicted value within 1 mo of HLT. The TLC in patients with primary pulmonary hypertension before surgery was close to the predicted value, but postoperative predicted TLC was achieved later than in emphysema patients. A donor-versus-recipient difference in TLC of more than 1L at the time of assessment did not influence the adaptation to the predicted value. FEV1 and vital capacity (VC) rose from means of 70% (SD = 25%) and 63% (SD = 20%) at 1 mo to 96% (SD = 27%) and 91% (SD = 18%), respectively, at 9 mo after HLT. After HLT, TLC returns to the predicted value for the recipient, and not to the preoperative TLC.(ABSTRACT TRUNCATED AT 250 WORDS)