Two typical cases of pure, isolated pnlmonic stenosis were studied by means of cardiac catheteriration during the past 12 months. On one of them the Brock type of valvulotomy was performed and this is the first case of pulmonic stenosis operated surgically in Korea. The results of the pulmonic valvulotomy was satisfactory initially. The patient had improved subjectively and venous pressure and circulation time returned to the normal level. However, 4 month postoperatively follow up study showed worsening of subjective symptoms again and re-catheterization was performed. There was an increased right ventricalar pressure. The reason of the failure of the operation was discussed.