Exercise capacity in cardiac transplanted patients has been reported to remain decreased in some studies; however, functional results after transplantation may vary, ranging from modest to spectacular improvement. The aim of the study was to quantify exercise capacity in a large series of transplanted patients and to search for factor predictive of a good functional result. Eighty-five patients (mean 52.1 +/- 11.8 years) underwent exercise testing with respiratory gas exchange measurements 1 to 100 months after transplantation. Mean performance was 112.4 +/- 33 W with a peak VO2 of 21.1 +/- 6 ml.min-1.kg-1. Heart rate was 103 +/- 14 at rest, reaching 142 +/- 22 beats.min-1 at the end of exercising. In univariate analysis, maximal or submaximal aerobic capacity parameters were strongly correlated with chronotropic reserve (r = 0.63; P < 0.001) without correlation with cold ischaemic time, number of rejection episodes or right bundle branch block. In multiple regression analysis, chronotropic reserve, time from transplantation, age of donor and age of patient were proved to be the variables best correlated with peak VO2. Our study confirms the persistence of a large decrease in aerobic functional capacity despite cardiac transplantation; limited exercise capacity does not improve over time, and is limited not only by the patient's age but by that of the donor, and especially by chronotropic reserve.