Background: Longitudinal median sternotomy is the most common surgical approach for access to heart disease treatment. The deep wound infections in postoperative period of cardiovascular surgery are a serious complication requiring high costs during treatment. Different studies have indicated some risk factors for the development of mediastinitis and preoperative variables are currently under investigation. Objective: The aim of this study is to identify the preoperative risk factors for postoperative development of mediastinitis in patients undergoing coronary artery bypass grafting and valve replacement. Methods: This observational study represents a cohort of 2768 consecutive operated patients. The period considered for analysis was from May 2007 to May 2009 and there were no exclusion criteria. Analysis was performed by univariate and multivariate logistic regression model of 38 preoperative variables. Results: Thirty-five (1.3%) patients developed mediastinitis and 19 (0.7%) associated with osteomyelitis. The patient age average was 59.9 +/- 13.5 years and the EuroSCORE of 4.5 +/- 3.6. Hospital mortality was 42.8%. The multivariate analysis identified three variables as independent predictors of postoperative mediastinitis: intra-aortic balloon pump (OR 5.41, 95% CI [1.83 -16.01], P = 0.002), hemodialysis (OR 4.87, 95% CI [1.41 to 16.861, P = 0.012) and extracardiac vascular intervention (OR 4.39,95% CI [1.64 to 11.761,P = 0.003). Conclusion: This study showed that necessity of preoperative hemodynamic support with intra-aortic balloon, hemodialysis, and extracardiac vascular intervention were risk factors for development of mediastinitis after cardiac surgery.