Background The aim of this study was to identify predictors of prolonged mechanical ventilation (PMV) following surgery for acute type A aortic dissection (AAAD) and to assess the influence of this complication on clinical outcomes. Methods and Results A total of 243 patients underwent emergency surgery for AAAD in the period of 1997-2006. Ten patients died within 48 h after surgery. The remaining 233 patients were divided into 2 groups according to the duration of mechanical ventilation; less than 48 h (group A: n=149) or 48 h or longer (group B; n=84). Multivariate analysis was used to identify predictors of PMV. Short and late outcomes were compared between groups. Multivariate analysis showed that shock (systolic BP <90 mmHg; p=0.007), postoperative renal dysfunction (creatinine >2.0 mg/dl; p=0.016), coronary artery bypass grafting (CABG) (p=0.017), and limb ischemia (p=0.044) were independent predictors of PMV. There was no significant difference in in-hospital mortality (group A, 2.7% vs group B, 3.6%) or 5-year survival (group A, 85.9% vs group B, 76.8%). Conclusions Shock, limb ischemia, CABG, and postoperative renal dysfunction increase the risk for PMV. Knowing the predictors of PMV should help optimize postoperative management of these patients. (Circ J 2008; 72: 1751 - 1757)