Introduction: We assumed that perioperative mortality risk scores (Euro I and II and STS) are related with aortic stenosis (AS) severity assessed by aortic valve area (AVA). Methods: We compared pre- and postoperative clinical and echocardiographic parameters with perioperative mortality in 337 consecutive patients undergoing AV replacement according with AVA: group 1 (area = 0.75 – 1 cm², n = 78) with group 2 (area < 0.75 cm², n = 259). Results: Mean age was 66 ± 12 vs 73 ± 9 years. Mean gradients were 50 ± 15 vs 60 ± 18 mm Hg; mean AVA was 0.83 ± 0.06 vs 0.61 ± 0.09 cm² (p < 0.001); indexed stroke volume was 41 ± 11 vs 46 ± 12 ml/m² (p < 0.001). Scores values were significantly greater in group 2 than group 1: Euro I 3.4 ± 3.4% vs 6.5 ± 9.3%, Euro II 1.5 ± 1.1% vs 3 ± 4.7%; STS 1.8 ± 1.3% vs 2.9 ± 2.4% (all p < 0.001). Postoperative mortality rate was 2.9%: 0% in group 1 and 3.4% in group 2 (p = 0.092). All scores were significantly greater in deaths vs survivors (Euro I 13 % vs 3%, Euro II 11 % vs 2% STS 5% vs 2%; p < 0.001). All scores were negatively correlated with AVA: r = – 0.242 (Euro I), r = – 0.235 (Euro II) and r = – 0.292 (STS); p < 0.001. Conclusions: Perioperative mortality risk and death rate seems to be related to AS severity in patients undergoing isolated AV replacement.