We have previously¹ isolated from porcine small intestine a peptide known as glicentin. The C-terminal portion of glicentin consists of the sequence of glucagon extended at its C terminus by an octapeptide^2,3, and differs slightly from the sequence of a proposed fragment of proglucagon⁴. Glicentin-like material has been demonstrated in the pancreatic A cell^5,6, wherein it is located in the periphery of the secretory granules⁷, whereas glucagon is located in the centre of the granules. To study the relationship of glicentin to the biosynthesis of glucagon, we have now investigated the glucagon-like and glicentin-like peptides in extracts⁸ and perfusates of the porcine pancreas. Our findings that a peptide with glicentin-like immunoreactivity, and intermediate in size between glicentin and glucagon, is secreted synchronously with glucagon suggest that this glicentin-related peptide is a major cleavage product of proglucagon.