Twelve patients with ventricular septal defect with pulmonary hypertension underwent lung biopsy to assess pulmonary obstructive vascular disease at the time of open heart surgery. According to the Heath and Edwards classification in grading of Pulmonary obstructive vasculr disease, there are eleven cases in grade 1 and one case in grade 3. Thickness of media was measured. It was expressed as percentage of medial thickness to outer diameter of artery. The medial thickness was correlated proportionally with elevation of pulmonary arterial pressure and pulmonary vascular resistance to systemic resistance ratio.