Epidemiological characteristics and risk factors related to infection in surgical sitesObjective: To identify the risk factors for infections in surgical sites, calculate length of procedures and validate the risk score National Nosocomial Infections Surveillance System (NNISS). Material and Methods: A cross-sectional study was conducted in a third level institution in 2009-2010 in 486 surgeries. Infections were classifi ed according to criteria of the Centers for Disease Control and prevention: primary superfi cial incisional, deep incisional and organ/space. NNISS risk was classifi ed by adding a point to ASA 3 or higher and/or contaminated or dirty wound and/or the time t above the 75 percentile. Results: The time t for the whole surgery was 107 minutes, the infection frequency was 10