A novel motilin analog peptide containing leucine instead of the usual 13th amino acid methionine, as in the naturally occurring motilin, is produced by gene recombination techniques in which several or identical genes, each coding for the novel peptide, are joined in series into a vector. The resultant recombinant DNA is introduced into Escherichia coli and the resultant transformant is cultivated. The resulting polymeric peptide can be cleaved to give the desired peptide.