Irritable bowel syndrome (IBS) is a chronic idiopathic alimentary tract disease of a functional nature. The original cause of IBS remains unknown. However, the functional intestinal disorders (associated with neurogenic and inflammatory factors) seem to usually result from complex general reasons, thus IBS pathogenesis should be investigated from the general – rather than local – perspective of the organism. The understanding of actual functions of the immune system, which exceed by far the defense role, has placed it in one line with endocrine and nervous systems, as guards of the homeostasis of the organism. Regulatory (CD4+ CD25+) T lymphocytes can inhibit in an antigen-nonspecific manner the proliferation and activity of effector CD4+ and CD8+ T lymphocytes, this way preventing the occurrence of auto-immune and inflammatory and allergic reactions. The aim of this study was an attempt in addressing the questions: are there any detectable differences in the magnitude of activation of regulatory T cells in IBS, as measured by the expression of selected receptor molecules? The test group was composed of 17 patients diagnosed in the Clinic of Gastroenterology and Metabolic Diseases in the Medical University of Warsaw, due to the irritable bowel syndrome. The material for cytometric testing was venous blood. The following parameters were subjected to immunological evaluation: percentage values of mononuclear peripheral blood cells [TCD4+ and TCD8+ lymphocytes with co-expression of CD28, CTLA-4 (CD152), CD69+, CD25+CD62L+, CD25+GITR receptor] and concentration of IL-1β, IL-1Ra (interleukin 1 receptor antagonist), IL-10 and TGF-β as determined by ELISA method. The observed quantitative and functional disorders of Tregs need confirmation and further testing on much broader panel of patients, in order to detect alterations specific for the 3 distinct forms of IBS (diarrhea, constipation-related and mixed).