The study centered on the possibility of surgery on the atrial septum (AS) without aortic clamping and cardiac arrest. We compared two groups of patients who underwent intervention on AS as the major or concomitant stage of surgical treatment. Nineteen patients were assigned to the main group; they were operated under CPB without aortic clamping and cardioplegia. The control group consisted of 20 patients, whose AS was surgically treated by using a standard technique with aortic occlusion. The groups were comparable by age and disease. The patients of both groups withstood the surgical interventions satisfactorily, with no mortality. The mean CBP time in the patients operated without aortic clamping was shorter than that in the control group patients (operated with aortic clamping) by about 18-20 minutes. The major surgical stage time did not differ between the groups. The technique of atrial septal defect closure or its dissection on the beating heart without cardioplegia is safe, comfortable for a surgeon and allows saving time required for the recovery period. Besides, it does not cause myocardial lesion associated with cardioplegia.