Many investigations habe been performed on left ventricular (LV) sstolic perfprmance in patients with atrial septal defect (ASD). However, few studies were done on LV diastolic properities in those with ASD. Therefore, we investigated the effect of right ventricular (RV) volume overload on LV diastolic function in patients with ASD. Twelve patients with ASD over 30 years old and age-matched normal controls (N) were included in this study. Patients with ASD were divided into two groups by Qp/Qs values (ASD1 : Qp/Qs<3, n=7