Guanylin, a 15-amino-acid peptide, is an endogenous ligand of the intestinal receptor guanylate cyclase-C. After binding to this receptor, guanylin increases the intracellular concentration of cyclic GMP and induces chloride secretion. We have isolated a genomic clone containing the entire murine guanylin gene. The guanylin gene is composed of three exons that span 1700 bp. The first 133 nucleotides of upstream promoter sequence lack the canonical TATA, CAAT, and SP1 elements. Guanylin transcription is nearly exclusively limited to the intestine, and the presence of guanylin mRNA is greatest in the distal colon and ileum. Therefore, characterization of the guanylin promoter is likely to provide another paradigm for intestine-specific gene regulation.