The results of surgical intervention are reported in 10 cases of critical valvular aorta stenosis diagnosed with echocardiography in neonatal age and infancy. The significance of echocardiography (2-dimensional, M-mode, Doppler) which does not mean stress for the patient in critical state and provides correct diagnosis is emphasized. Correct diagnosis contributes to the performance of operation in appropriate time as well as the use of immediately performable and correct surgical technique is considered necessary. These are the first cases in Hungary where open heart operations have been carried out on the basis of echocardiography in neonatal age and infancy. The good results proved the adequacy of the solution.