Summary. The purpose of this study was to evaluate children who underwent balloon valvuloplasty due to critical aortic ste- nosis following clinical (low cardiac output, cardiogenic shock, congestive heart failure) and echocardiographic criteria (morphological evidence of left ventricular hypertrophy, with depression of left ventricular function, irrespective of transvalvular gradient). We assessed the effectiveness of balloon valvuloplasty in 5 children (all male) who were submitted to aortic valve balloon dilatation over 3.5 years (10.1998–05.2003). The age at dilatation was 29±24days, BW 3.92±0.82 kg and BSA 0.24±0.03 m2. In all children the balloon valvuloplasty was performed with manual inflation of balloon at 4–6 bars through the femoral artery. The mean systolic pressure gradient across the aortic valve decreased from 68±20.5 mmHg to 9±10.95 mmHg, i.e. by 85%, (p<0.01). Aortic valve ring diameter was 9.2±0.84 mm, and balloon/aortic ring ratio 0.8±0.04. The degree of aortic insufficiency immediately after the dilatation did not significantly increase. Dilatation was performed without complications. Long term results were evaluated in all patients 3.2 – 54 months after valvuloplasty and revealed the continuously increasing residual aortic valve gradient (Doppler measurement) 33±10.95 mmHg to be significantly lower (p<0.01) than before valvuloplasty. None of the children was showing clinical symptoms of the disease. According to echocardiographic analysis two of them developed aortic valvar insufficiency grade II, two had trivial insufficiency, one was without insufficiency. One child is an candidate for the Ross procedure in future (gradient 50 mmHg, insufficiency grade II, age 4.5 years.). Balloon valvuloplasty provides effective interventional method in the treatment of the neonates and infants with critical aortic stenosis.