Objective: This study aims to fine-tune the decision making for ascending aorta treatment in bicuspid aortic valve surgery. Methods: A total of 1693 patients with a primary indication for aortic valve surgery were investigated retrospectively with respect to a multifactorial decision-making policy including the z score and the clinical outcome in relation to different techniques for ascending aorta treatment (no intervention n = 1116; intervention n = 577 either by ascending aorta replacement n = 404 or aortoplasty n = 173). Follow-up was 99.5% complete (mean 7.0 ± 4.4 years, range 0-17.7 years, 11,895 patient-years). Results: Hospital mortality was 1.2% for the no-intervention group and 0.9% for the intervention group and was not different between groups (P =.629). Survival compared with the adjusted normal population was lower for both groups (no intervention: P <.001) but not by such a great margin for the intervention group (P =.27). Determinants for death were not related to the ascending aorta treatment. Aortoplasty led to significantly more reoperations (P =.002). The z score thresholds for intervention on the ascending aorta were greater for younger patients, intervention was more liberal in young age, depicted in nomograms. Conclusions: In our study, ascending aorta intervention could be performed with low hospital mortality and obviously did not add to the overall mortality compared with no intervention. Ascending aorta replacement was the most definite intervention. The multifactorial decision for ascending aorta intervention including the z score of the ascending aorta was more liberal in younger patients compared to the simple aortic size guidelines and provided excellent results. However, generalizability needs further data.