Backgrounds: The optimal timing of surgical intervention remains controversial in asymptomatic patients with severe aortic stenosis (AS), and we tried to compare long-term results of early surgery to conventional treatment strategy based on current guidelines. Methods: From 1997 to 2005, we prospectively included a total of consecutive 224 patients(114 men, age;60짹11 yrs) with severe aortic stenosis, and the exclusion criteria were defined as the presence of angina, syncope, exertional dyspnea, ejection fraction(EF)<0.50, significant mitral valve disease and age>85 yrs. Severity of AS was assessed by echocardiography, and AS was graded as severe and very severe when aortic valve (AV) area<1.0 cm2 and <0.75 cm2, respectively. Cardiac events were defined as the occurrences of cardiac death and congestive heart failure admission. Results: Early surgery was performed on 67 patients(group A), and conventional strategy was chosen on 157(group B). There were no significant differences between the two groups in terms of age, gender, Euroscore, but the incidence of very severe AS was significantly higher in the group A(p<0.01). There was no operative mortality and 1 late cardiac death in group A, and 17 cardiac deaths and 7 CHF admission in group B. The cardiac event rate was significantly lower in group A than group B(p=0.002). In patients with very severe AS, the group A showed the significantly lower cardiac mortality rate (0% vs. 8짹5%, p=0.004) and event rate(0% vs. 23짹6%, p=0.0008) at 6 yrs, but the 6 yr cardiac mortality(9짹9% and 9짹3%) and event rates(9짹9% and 15짹5%) were similar between the two groups in severe AS. In group B, 74 patients underwent late AV replacement during follow-up and the survival rates free of cardiac events or surgery were 79짹3% at 2 yrs, 57짹4% at 4 yrs, and 39짹5% at 6 yrs. The survival rates free of cardiac events or surgery in patients with bicuspid AV were significantly lower than those in patients with the other cause(p<0.05). Conclusions: The clinical outcomes were different according to severity and causes of severe AS, and early surgery can be a therapeutic option to further improve clinical outcomes for asymptomatic patients with very severe AS and low operative risks.