INTRODUCTION: Heart transplantation has become an increasingly acceptable therapeutic option for pediatric patients with end-stage heart disease. With advances in surgical technique, immunosuppressive therapy and follow-up care, long-term survival and health-related outcomes need to be assessed. We report the results of serial exercise testing performed over a 5-year period using stress echocardiography in a cohort of pediatric heart transplant patients (HTP) that we follow. METHODS: HTP (n=7) exercised on a semi-recumbent cycle ergometer with the workload increased in 20-40 watt increments every 3 minutes until volitional fatigue. Echocardiography-Doppler measurements, heart rate and blood pressure were taken during each stage. Results were compared with healthy controls (CON, n=12). Median values over the 5-year period are reported. RESULTS: Patient demographics including age, height, and weight were similar between HTP and CON. The resting left ventricular end-diastolic (3.6 vs 4.4 cm, p<0.0001) and end-systolic (2.1 vs 2.7 cm, p<0.0001) dimensions and the aortic cross-sectional area (2.5 vs 3.7 cm²) were smaller in HTP. The stroke volume index (36 vs 49 mL/m², p<0.003), cardiac index (5.55 vs 9.03 L/min/m², p<0.0001), and heart rate (169 vs 185 bpm, p>0.05) were lower in HTP at peak exercise. Although measures of contractility were similar, ejection force (25.5 vs 55.3 cm•g/s², p<0.009) and work (984 vs 1219 J/kg, p<0.008) were lower in HTP at peak exercise. CONCLUSIONS: Exercise tolerance is reduced in heart transplant patients. Both central and peripheral limitations may be responsible. Over time, hemodynamics and ventricular function have remained relatively constant in our cohort.