Patients with end-stage pulmonary and pulmonary vascular disease can now be offered single-lung (SLT), double-lung (DLT), or heart-lung (HLT) transplantation. Long-term survival with greatly improved pulmonary function has been reported with all three procedures. Little has been reported of the exercise capacity after transplantation. This report documents Stage 1 exercise test results in six SLT (five males and one female; age 50.7 +/- 4.4; FEV1.0 75.5 +/- 6.7% of predicted) and seven DLT (three males and four females; age 37.3 +/- 6.7; FEV1.0 85.1 +/- 10.3% of predicted) recipients, early (3 months) and late (1 to 2 yr) following transplantation. The results show low work rates and VO2max in both SLT and DLT recipients at 3 months after transplant. Heart rate and minute ventilation did not appear limiting. There was no significant improvement when retested 1 to 2 yr after transplant. At 3 months, VO2max was 46% of predicted for SLT and 50% of predicted for DLT recipients. It is concluded that considerable exercise limitation persists after transplantation and does not appear to improve with time. These limitations are similar for both SLT and DLT and are not related to ventilation. The results may suggest chronic muscle deconditioning after long-term pretransplant debilitation.