The purpose of this research is to study the effects of the Probiotics in decreasing surgical site infection after colectomy. Eighty patients above 13 years of age and with colorectal cancer, who referred to Razi, Golestan and Emam Khomeini Hospitals during two years of 1390 and 1391, were classified into two groups of "intervention" and "control" by block randomization. The following were excluded from the trial: critically ill patients, patients with central venous catheter, disrupted mucosal barrier, short bowel syndrome, abnormal cardiac valves, prosthetic valves or joints. Those patients of "intervention" group received England-made Balance Capsules; and patients of "control" group received Placebos, both of which were taken 2 doses daily in the period from four days before operation and ten days after. WBC diff, CRP, IL6, and TNF-a in the patients of both groups were checked at the beginning of the observation and 72 hours after operation. And their temperature, pulse rate, respiratory rate, and blood pressure were checked at the beginning of the research and then the first, second, third, tenth and thirtieth day after operation. Likewise, the creation of cellulitis and purulent discharge from operation area in the patients were evaluated at the first, second, third, tenth, and thirtieth day after operation. In addition to the above, mortality, the necessity for admission to ICU and the related duration were evaluated, too.