Trefoil peptides (TFFs) with a unique trefoil domain(s) are presumed to function in protection and repair of the gastrointestinal epithelial layer. Three peptide family members are differently distributed in the mouse gastrointestinal tract: TFF1/pS2 specifically in stomach, TFF2/SP mainly in stomach, pancreas and duodenum, and TFF3/ITF in intestine. We cloned and sequenced the mouse TFF1 gene 5'-upstream region by means of the genomic walking procedure. The cloned region was ligated to the luciferase reporter gene and then introduced into mouse gastric surface mucous GSM10 cells which express TFF1 and TFF2. The minimum promoter was located in the region containing the TATA-box between −39 and the transcriptional start site. Further upstream regions stimulated (−2192— −1630bp, −641— −243bp, −137— −39bp) and inhibited (−1630— −641bp, −243— −137bp) luciferase gene expression. These regions as well as short segments conserved in the mouse and human 5'-upstream sequences may be important for modulation of the mRNA level of the TFF1 gene.