Background. The aim of this study was to examine the impact of prolonged intensive care unit (ICU) stay on in-hospital mortality and long-term survival. Methods. Prospectively collected data from 6,101 consecutive patients who underwent surgery between 2003 and 2007 were analyzed. Prolonged ICU stay was defined as a total duration of ICU stay of 3 days or more postoperatively, including readmissions; patients with an ICU stay less than 3 days were identified as controls. Univariate and multiple variable analyses were performed to identify risk factors associated with prolonged ICU stay. Results. Of 6,101 patients, 1,139 (18.7%) patients had a prolonged ICU stay. These patients had a higher ICU mortality (10%) compared with controls (0.6%; p < 0.001). On discharge from the ICU, their hospital mortality was still 6-fold higher (1.2%) compared with controls (0.2%; p < 0.001). Finally, the patients who had prolonged ICU stays had lower survival after discharge from the ICU-89.2% and 81.2% at 1 year and 3 years, respectively, compared with 97.8% and 93.6%, respectively, for controls (p < 0.001). Multiple variable analysis revealed prolonged ICU stay to be an independent predictor of prolonged hospital stay, higher hospital mortality, and poorer long-term survival (all p < 0.001). Conclusions. Prolonged ICU stay is an important predictor of adverse immediate, short-term, and long-term outcomes after cardiac operations. (Ann Thorac Surg 2012;94:109-16) (C) 2012 by The Society of Thoracic Surgeons