This study elucidates the significance of Toll-like receptor 4 (TLR4), CD14, and nuclear factor (NF)-κB on the pathogenesis of ulcerative colitis (UC). Colonic biopsy specimens were collected from active UC and controls. The expression of TLR4, CD14, and NF-κBp 65 was analyzed by immunohistochemistry (IHC) and reverse-transcription polymerase chain reaction (RT-PCR). In UC, disease activity index (DAI) and pathological grade were classified according to the Powell-Tuck grade system and Truelove-Richards system, respectively. Fifty-six UC cases and 56 controls entered the investigation. IHC and RT-PCR revealed a significant increase of TLR4, CD14, and NF-κBp 65 antigen expression in colonic mucosa of UC compared with colonic mucosa of controls (p < .001). In UC, TLR4, CD14, and NF-κBp 65 expression were positively related to DAI (r = .873, p < .001; r = .576, p < .001; r = .747, p < .001 receptively). NF-κBp65 significantly correlated with TLR4 and CD14 (r = .669, p < .001; r = .576, p < .001, receptively). TLR4, CD14, and NF-κBp65 were positively related to pathological classification in UC (p < .01). Thus, TLR4, CD14, and NF-κBp65 were upregulated significantly in UC, to an extent that reflects the degree of inflammation and thereby might contribute to the occurrence and development of UC.