The present work deals with the synthesis of a hydrophobized peptide and its localization at the membrane surface, after its incorporation into phospholipid vesicles. The tetrapeptide, Trp-Met-Asp-Phe-NH2, which corresponds to the C-terminus of the cholecystokinin/gastrin hormone family, is conjugated to N-glutaryldioleoylphosphatidylethanolamine using a carwbodiimide-catalyzed reaction method, Sonication of the lipophilized hormone in the presence of dimyristoylphosphatidylcholine results in a strong sequestration of the conjugate in the artificial membrane structures that are formed, More detailed information on the localization of the peptide moiety with respect to the membrane surface is gathered from fluorescence measurements. Both the observed blue shift in the fluorescence spectra and the quenching of Trp emission in the presence of potassium iodide point to a partial screening of the hormone moiety from the surrounding aqueous phase. The different parameters that may influence the physicochemical behavior of a hydrophobized peptide in a membrane structure are briefly discussed.