Background: common post-operative complications. Apart from bacterial contamination of wound, various patient and environment related factors play role in development and outcome of SSI. The present study is undertaken to study the frequency of SSI with reference to factors contributing to it and the antimicrobial susceptibility pattern of the causative organisms. Methods: This single-observer, cross-sectional, complete-enumeration prospective study was carried out over a period of one year (from March 2012 to Feb 2013) in the department of Surgery at Department of General Surgery, Lord Buddha Koshi Medical College & Hospital, Saharsa, Bihar. 196 pus samples from cases of surgical site infections were processed for gram staining, culture, biochemical identification tests and antimicrobial susceptibility testing. Methicillin-Resistant Staphylococcus aureus (MRSA) strains were detected by using oxacillin and cefoxitin disk diffusion and minimum inhibitory concentration (MIC) of oxacillin was tested by broth dilution technique. Results: The overall frequency of SSI was 6.17%. Most common isolates were Staphylococcus aureus, coagulase negative Staphylococci (CONS), E. coli and Pseudomonas aeruginosa. The frequency of MRSA was 8.6%. The maximum frequency was among patients operated on emergency basis in surgical department. Conclusions: The most important determinants for SSI were emergency surgery and presence of co-morbid conditions. The frequency of occurrence was age-dependent, with maximum rate of SSI in males and females in the third and sixth decades of life, respectively.