The aim of this study was to determine the SSI incidence in surgical wards of Polish hospitals which participate in the Active Surveillance of Nosocomial Infections System with consideration of the character of the surgical ward. Data in this thesis originate from 25 hospitals which have surgical wards and which participated in the Active Surveillance of Nosocomial Infections System in the period from January 2002 and December 2003. During the analysed period there were 57 857 surgical procedures performed and 1259 cases of SSI registered. General incidence rate of SSI was 2.18 for each 100 analysed procedures. The highest incidence rate as compared to the surgical wards of other profile was observed in the general surgery departments – 3.39%. The risk factors that influenced SSI: patients over 65 year of life; ASA above 2, the procedure performed in contaminated or dirty operating fields, emergency procedures and multi-procedure surgery, pre-surgery hospitalization lasting over 2 days. The dominant pathogens of SSI were: Staphylococcus spp., Enterococcus spp., E.coli. Surgical site infections were the most frequently registered form of nosocomial infections on surgical wards of Polish hospitals which participated in the Active Surveillance of Nosocomial Infections System. The incidence rates in Polish hospitals were comparable to data obtained in other national research programmes.