The purpose of the study – to study the association of the polymorphic variant C-159Tof the CD14 gene in patients with irritable bowel syndrome (IBS) depending on thepredominance of diarrhea or constipation in the clinical course and the relationshipbetween genotypes of the CD14 gene (C-159T) and some blood parameters.Material and methods. The study involved 90 patients with IBS (30 men and 60women aged 22 to 56 years). The polymorphic variant of the CD 14 gene (C-159T)was analyzed by polymerase chain reaction in 90 patients with IBS without and withconcomitant obesity and 30 people in the comparison group. Blood levels of C-reactiveprotein (CRP), tumor necrosis factor α (TNFα), transforming growth factor β1(TGFβ1), interleukin-10 (IL-10), 8-isoprostane, ceruloplasmin, medium molecules andcalprotectin levels in feces were determined.Results. In patients with IBS and obesity, the frequency of TT genotype (36.7%) washigher compared to healthy subjects (TT genotype – 13.3%). Significantly higherserum levels of CRP (3.5 times and 26.7%), TNFα (1.7 times and 19.5%), TGFβ1(29.8% and 19.2%), 8-isoprostane (54.1% and 31.9%), ceruloplasmin (56.7% and33.0%), medium molecules (7, 5% and 12.9%) and calprotectin (55.7% and 37.4%) inthe feces compared to the CC and CT genotype have been determined in patients withIBS, combined with obesity, TT genotype with a predominance of diarrhea.Conclusions. The association of a polymorphic variant of the CD14 (C-159T) gene withthe risk of IBS development in obese patients has been established. The TT genotype ischaracterized by a higher content of proinflammatory cytokines (TNFα), lower levelsof anti-inflammatory cytokines (IL-10), increased CRP, more pronounced changesin the prooxidant and antioxidant blood systems (higher levels of 8-isoprostane andceruloplasmin, local inflammation (increase in calprotectin content) and severity ofendotoxicosis (higher content of medium molecules).