Résumé : The acid extract of a liver metastasis from a patient with elevated plasma motilin levels contained large quantities of motilin (3.37 μg/ml). The extract was concentrated on a C18-column and motilin was isolated by gel chromatography (Sephadex G-50) followed by cation ion exchange chromatography (HR5/5 Mono-S) and three successive steps of reverse phase chromatography (Nucleosil 300-5 C18). The pure peptide was sequenced and the identity of porcine and human motilin was confirmed. This is the first report of a tumor containing large amounts of motilin.