At a cardiosurgical department in Brno in 1978-1987 244 patients above 15 years of age were operated for the first ++time on account of inborn heart disease. This number comprised 21 patients (8.6%) with incomplete defects of the atrioventricular septum. Two patients died in the early postoperative period, two patients were lost from the records and 17 patients were subjected to clinical and echocardiographic examination two to 11 years after operation. All patients were in the 1st or 2nd functional class of the NYHA classification, signs of recanalization were found in one patient and progressing mitral regurgitation in two patients. Consistent with data in the literature, the authors consider it important, to check the patients regularly, incl. clinical and echocardiographic examination, after operations of incomplete defects of the atrioventricular septum and to focus special attention of progressing mitral regurgitation.