The persistence of right ventricular dilatation and paradoxical interventricular septal motion are two echocardiographic abnormalities rarely reported after surgical closure of atrial septal defects. The aim of this study was to identify the predictive factors of these abnormalities in the long-term and to study their functional consequences. One hundred and two patients aged 18 +/- 14 years (range 1-62 years) underwent closure of atrial septal defects. Thirty-five patients were under 10 years of age, 33 were 10 to 20 years of age and 34 were over 20. Fifty-six patients were female. The rhythm was sinus in the great majority of cases (97%). Three patients, all over 40 years of age, were in atrial fibrillation. Before surgery, right ventricular dilatation was observed in 95 patients (91.2%), paradoxical septal wall motion in 93 patients (91.2%), the ratio of pulmonary/systemic output was 2.7 +/- 0.6 (range 1.7 to 7.4) and over 2 in 90% of patients: pulmonary systolic pressure was 32.3 +/- 12 mmHg and over 40 mmHg in 18 patients (17.6%). Ninety-four patients were followed up regularly with a mean follow-up time of 5.5 +/- 3.6 years (1-14 years). The right ventricle remained dilated in 37 patients (39.4%) after surgery: the right ventricular dimension decreased from 36 +/- 1 to 27.8 +/- 6.2 mm (p = 0.001). The ratio of end diastolic right ventricular/left ventricular dimension also decreased from 1.07 +/- 0.31 to 0.56 +/- 0.12 (p = 0.0001). Multivariate analysis identified two predictive factors of persistent right ventricular dilatation: age > 40 years (p = 0.009) and a pulmonary/systemic flow ratio > 3 (p = 0.03). Interventricular septal wall motion remained paradoxical in 21 patients (22%). Multivariate analysis identified two predictive factors of persistent paradoxical septal motion: age > 40 years (p = 0.02) and systolic pulmonary pressures > 40 mmHg (p = 0.03). These abnormalities remained asymptomatic in all but two patients with persistent long-term hypertension and a residual atrial septal defect. The persistence of right ventricular dilatation and paradoxical septal motion was quite common, with older age at surgery, systolic pulmonary artery pressure > 40 mmHg and a ratio of pulmonary/systemic blood flow > 3, being predisposing factors. These abnormalities were clinically asymptomatic when isolated.