. The activity of a non-invasive marker of inflammation in the colon is used to evaluate the clinical, endoscopic and biological characteristics of ulcerative colitis and colon polyps. In this study, the authors studied the possibility of using non-invasive marker – a faecal calprotectin as a highly sensitive method in the activity of the inflammatory process in the colon. The study included 40 patients with ulcerative colitis and colon polyps, which a colonoscopy was performed. The concentration of calprotectin in stool samples was determined in all patients and was evaluated according to the clinical activity of the disease. A significant increase in the level of calprotectin in patients with colon polyps 42±5,6 µg/g wasn’t revealed. On the contrary, the concentration of a faecal calprotectin was significantly higher in patients with ulcerative colitis. This concentration increases in patients with a high degree of inflammatory activity and length of lesions of the mucous membrane of the colon. The concentration of calprotectin level correlates with the extent of lesion and activity of the inflam-matory process in the colon, but not with endoscopic activity of ulcerative colitis. The use of modern method of non-invasive diagnostic marker of the inflammatory process in the intestine allows to diagnose functional and organic pathologies of the colon without the supplementary instrumental methods.