The role of mucosal fibroblasts in intestinal inflammatory reactions is not known. In this study, we demonstrate that fibroblasts grown from histologically normal human duodenal biopsy tissues expressed mRNA genes for granulocyte‐macrophage colony‐stimulating factor (GM‐CSF). IL‐lα, IL‐1β, IL‐6, IL‐8, IL‐10, intercellular adhesion molecule‐I (ICAM‐I) and vascular cell adhesion molecule‐1 (VCAM‐i) when stimulated with lipopolysaccharide (LPS) or IL‐1α. The increased mRNA expression of GM‐CSF, IL‐1α IL‐1β IL‐6 and IL‐α in response to IL‐1α and LPS stimulation was time‐ and dose‐dependent. In contrast. IL‐10 was weakly expressed when fibroblasts were stimulated with LPS. IL‐1α or tumour necrosis factor‐alpha (TNF‐α), but the expression was enhanced in the presence of cycloheximide combined with optimal concentrations of LPS. IL‐1α or TNF‐α. IL‐1α was a more potent stimulator than LPS for GM‐CSF. IL‐6, IL‐8 and I L‐10 expression, but not for IL‐1α and IL‐1β. Increased GM‐CSF. lL‐6 and IL‐8 gene expression was associated with the production of cytokine proteins in culture supernatant, but IL‐1α and IL‐1bL remained undetectable. Dexamethasone suppressed both gene expression and protein production of GM‐CSF. IL‐6 and IL‐8 when fibroblasts were exposed to IL‐1α. TNF‐α stimulated the release of GM‐CSF. IL‐6 and IL‐8 and, combined with IL‐1α. cytokine production was enhanced synergistically. Finally, both LPS and IL‐1ã up‐regulated ICAM‐I and VCAM‐1 gene expression. These findings implicate duodenal fibroblasts in the initiation and/or regulation of intestinal inflammation.