PURPOSE: We investigated the relationship between severity of pulmonary regurgitation (PR), exercise capacity, right ventricular (RV) volume overload and RV function in the patients with long-term follow-up after repair of tetralogy of Fallot (TOF). METHODS: To evaluate exercise capacity, cardiopulmonary exercise test (CPX) was performed in 26 patients and 18 normal controls on a treadmill, and maximal oxygen consumption (VO(2max)) and anaerobic threshold (AT) were compared among the two groups. To assess severity of PR, RV volume and function, magnetic resonance imaging (MRI) study was performed in the patient group and the PR fraction (%), RV end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction(EF) were measured. Patient group was divided into two subgroups by age and influences of PR on RV volume and function were compared among these subgroups. RESULTS: VO(2max) and AT were significantly decreased in the patients in comparison to the control subjects (28.9+/-10.4 vs 38.1+/-9.9 ml/kg/min, P=0.01; 0.98+/-0.53 vs 1.44+/-0.59 l/min, P=0.03). PR fraction inversely correlated with the VO(2max) (r=-0.58, P<0.01) and had a tendency toward inverse correlation with AT (r=-0.35, P=0.15). In young age group less than 15 years, no significant correlation between RVEDV, RVESV, corrected QRS duration (cQRS) and PR fraction (r=0.48, P=0.19; r=0.45, P=0.22; r=0.12, P=0.76) was observed, but in old age group, RV volume (RVEDV: r=0.73, P=0.01; RVESV: r=0.61, P=0.04) and the cQRS (r=0.66, P=0.03) were increased according to the severity of PR. RVEDV and RVESV showed inverse correlations with RVEF (r-0.59, P=0.003; r= -0.78, P<0.001), and RVEF showed positive correlation with VO(2max) (r=0.62, P=0.04). CONCLUSION: Patients in long-term follow-up after repair of TOF showed impaired exercise capacity than normal subjects. PR has a negative influence on the exercise tolerance in this group of patients, and the deleterious effects of PR on RV volume and QRS prolongation may related with the age and/or duration of PR. RV volume overload may deteriorate RV function and cause resultant exercise impairment.