Physical working capacity and cardiovascular response to graded exercise on a bicycle ergometer were investigated in 70 children and adolescents (33F, 37M) after renal transplantation. Results of static and dynamic lung function tests were within the normal range in all patients. Systolic blood pressure, heart rate, pulmonary ventilation and oxygen uptake increased with workload and returned to pre-exercise levels after 5 m of rest. During exercise, blood pressure values were within the normal range in almost all patients. The increase in heart rate and respiratory frequency was blunted in patients receiving beta blocking agents. Maximum workloads (Wmax) were 2.00 +/- 0.48 W/kg in females and 2.38 +/- 0.54 W/kg in males, which are 78 +/- 18% and 84 +/- 18% of the normal values predicted for age. Maximum oxygen consumption (VO2max) was 23.2 +/- 5.8 ml/min/kg in females and 28.3 +/- 5.8 ml/min/kg in males. Half of the patients had height below the third percentile. For this reason exercise capacity in relation to height is probably a more relevant parameter than age. Using actual height, Wmax was 102 +/- 20% and 102 +/- 29%, and VO2max 74 +/- 14% and 80 +/- 18% of predicted values, respectively. We conclude that the adaption of the cardiovascular and respiratory system to graded exercise was influenced by beta blocking agents. Wmax and VO2max were significantly reduced for age in pediatric patients after renal transplantation. Wmax was normal, but VO2max was still reduced if corrected for height.