Objective: The aim of this study was to calculate the incidence of pulmonary hypertension and its age distribution in isolated atrial septal defect (ASD) patients in our population. Methods: A total of 124 ASD (secundum type) patients were included in the study. The diagnosis was made with echocardiography. Pulmonary artery systolic pressure was obtained by Doppler echocardiography. Mean pulmonary artery pressure (mPAP) was estimated with the relation of MPAP to PASP as (mPAP = 0.61×PASP + 2 mm Hg). Results: Severe PA hypertension (mean pressure > 40 mm Hg) was found in 12 patients (9.67%), age range was neonate to 60 years but most of them were less than 30 years old. Conclusion: It was seen that pulmonary pressure increases with age.