BACKGROUND/AIMS: We investigated the mRNA expression of spectrum of cytokines in the colonic mucosa in inflammatory bowel disease (IBD). METHODS: The expression of cytokine gene was evaluated by using the reverse transcription-polymerase chain reaction and the radioactivity of amplified cDNA standardized by coamplified beta-actin cDNA. RESULTS: Crohn's disease and ulcerative colitis showed significantly increased expression of IL-1beta, IL-6, IL-8 and TNF-alpha mRNA as compared with controls (p < 0.05). CONCLUSION: Proinflammatory cytokines such as IL-1beta, IL-6, IL-8 and TNF-alpha are closely involved in the immune abnormalities of inflammatory mucosal lesions in IBD.