Background/Aims: Lipopolysaccharide (LPS) is a molecule formed by lipids and polysaccharides and is the major cell wallcomponent of gram-negative bacteria. High LPS levels are known to block CD26 expression by activating Toll-like receptor 4. The aim of this study was to correlate the serum levels of LPS and CD26 in Crohn’s disease (CD) patients with serum levelsof C-reactive protein (CRP), interleukins, CD activity index, and tumor necrosis factor-α (TNF-α). Methods: Serum sampleswere collected from 27 individuals (10 with active CD, 10 with inactive CD, and 7 controls) and the levels of LPS, CD26, TNF-α,interleukin-1β (IL-1β), IL-6, IL-17, and CRP were determined by enzyme-linked immunosorbent assay. The levels of LPS andCD26 were then tested for correlation with TNF-α, IL-1β, IL-6, IL-17, and CRP. Results: Serum levels of LPS were significantlyelevated in the active CD group (P =0.003). Levels of IL-1β (P =0.002), IL-6 (P =0.003), and IL-17 (P <0.001) were lower in theCD groups. Serum TNF-α levels were increased in the active CD group. The CRP levels were elevated in the CD groups whencompared to controls (P <0.001). The CD26 levels were lower in the CD groups than in the control group (P <0.001). Among thevariables analyzed, there was a correlation between LPS and CRP (r=–0.53, P =0.016) in the CD groups. Conclusions: Individualswith CD exhibited higher serum levels of LPS varying from a 2- to 6-fold increase depending on disease activity, when comparedwith healthy controls. CD26 levels were lower in the CD groups. Both LPS and CD26 correlated with disease severity andserve as potential CD biomarkers.