Summary Aim The aim of the paper was to conduct a retrospective analysis of a group of patients after surgery for colorectal cancer: to define aetiological factors for, and assess drug-sensitivity of bacteria causing infection. Materials/Methods Between January 2000 and June 2004, 350 patients underwent surgery for colorectal cancer. Within that group 17 (4,86%) patients developed postoperative wound infections within 30 days of the operation. In all cases we performed microbiological examinations. All the cases of infections were analysed, with special attention being paid to the following groups of risk factors: patient-related and perioperative procedures. Results In all, 17 cases of superficial infections were identified within the skin and subcutaneous tissues. The most frequently identified aetiological factors were colibacillus species and Enterococcus faecalis. Targeted antibiotic therapy was applied, based on the results of antibiograms. Rapid recovery was observed in all patients. The most important patient-related risk factors included: BMI over 25 kg/m 2 in 11 (64.7%) patients, high (3 rd) degree of neoplastic advancement in 13 (76.5%) patients and preoperative radiotherapy in 7 (41.2%) patients. All infections were found in patients after resection of the sigmoid colon or rectum. Conclusions The most frequent aetiological factor identified, on the basis of cultures, was bacterial fl ora of the colorectum. 1. The most important risk factors include: degree of neoplastic advancement, obesity and preoperative radiotherapy. 2. The application of appropriate systems for the preparation of the patient during the perioperative period has a great infl uence on the frequency of infections. 3. Because high drug-resistance in bacterial cultures is a real possibility, it is essential to perform antibiograms in order to help select the most appropriate antibiotics for the treatment of infections.