Congenital mitral stenosis is a rare cardiac lesion which frequently associated with other congenital anomalies of the heart and great vessels. There are many difficulties in its preoperative diagnosis and choice of adequate treatment. We present two cases of congenital mitral stenosis who have had operated in this hospital at March 1981 and January 1983. One was 13 years old female with isolated, type III mitral stenosis who had mitral valve replacement with Ionescu-Shiley bioprosthetic valve, the other was 2 years and 3 months old female with supramitral ring associated with VSD and PDA who had operation of resection of supramitral ring and repair of associated lesions. Postoperative course of both cases is excellent except one episode of sudden supraventricular tachyar-rhythmia on latter case and it was controlled by medical treatment. [KTCS 1983;1:3-9]