<jats:p>Two peptides with tachykinin‐like ability to contract longitudinal muscle from the guinea pig ileum were isolated from the intestine of the common dogfish, <jats:italic>Scyliorhinus caniculus</jats:italic>. The amino acid sequence of scyliorhinin I was established as Ala‐Lys‐Phe‐Asp‐Lys‐Phe‐Tyr‐Gly‐Leu‐Met‐NH<jats:sub>2</jats:sub> and this peptide cross‐reacted with antisera directed against the C‐terminal region fo substance P. The amino acid sequence of scyliorhinin II was established as Ser‐Pro‐Ser‐Asn‐Ser‐Lys‐Cys‐Pro‐Asp‐Gly‐Pro‐Asp‐Cys‐Phe‐val‐Gly‐Leu‐Met‐NH<jats:sub>2</jats:sub> and this peptide cross‐reacted with antisera directed against the C‐terminal region of neurokinin A. The mammalian peptides substance P and neurokinin A were absent from the dogfish intestinal tissue.