BACKGROUND The aim of this study was to assess the utility of Doppler echocardiography both at rest and during isotonic exercise in evaluating competition eligibility of patients with repaired coarctation of the aorta (CoAo). METHODS Seventeen young patients (11 male, 6 female; mean age 17.1 +/- 7.9 years) with previous surgical repair of CoAo were examined. Mean follow-up after repair was 10.3 +/- 3.5 years. All patients underwent complete Echocardiographic examination (M-mode, 2D and Doppler) and an exercise test on an ergometric bicycle, with continuous wave Doppler monitoring of flow velocity in descending aorta, with a transducer positioned in the suprasternal notch. Peak and mean Doppler gradients in descending aorta were measured both at rest and during exercise, using the simplified Bernoulli equation. According to peak Doppler gradient at rest, patients were divided into two subgroups: Group IA = patients with peak gradient lower than 25 mmHg; Group IB = patients with peak gradient greater than 25 mmHg. Finally, 17 healthy subjects (Control Group), matched for age and body surface area, were examined. RESULTS Systolic and diastolic blood pressure both at rest and during exercise were not significantly different in the 3 groups. Patients of Group IB showed a significant increase of left ventricular mass (124.0 +/- 24.4 vs 85.8 +/- 24.1 g/m2, p < 0.01), and during exercise, a significant increase of peak gradient (68.3 +/- 27.2 vs 23.5 +/- 9.0 mmHg, p < 0.0001) and mean gradient (34.8 +/- 11.5 vs 11.9 +/- 5.0 mmHg, p < 0.0001) at the level of the descending aorta. In patients of Group IA, echocardiographic parameters were not different in comparison with the Control Group, whereas Doppler gradients during exercise were only slightly greater than those observed in the Control Group (peak gradient 36.9 +/- 13.0 vs 23.5 +/- 9.0 mmHg, p < 0.05; mean gradient 19.6 +/- 6.0 vs 11.9 +/- 5.0 mmHg, p < 0.05). However, 4 patients of Group IA showed a peak gradient during exercise greater than 40 mmHg (this value was equivalent to the mean value plus 2 Standard Deviations, observed in the Control Group) with the presence of diastolic flow, whereas exercise systolic blood pressure was lower than 200 mmHg. CONCLUSIONS Thus, as a result of this study aimed at evaluating competition eligibility in patients with repaired CoAo, two subgroups of patients have to be distinguished according to Doppler echocardiography results: a) patients with peak Doppler gradient at rest greater than 25 mmHg, for whom competition is forbidden; b) Patients with peak gradient lower than 25 mmHg who must be investigated with exercise Doppler echocardiography to exclude an abnormal increase of Doppler gradients, even if exercise blood pressure is within normal limits.