A number of peptide hormones have been shown to contain amphipathic helical segments capable of binding to phospholipids. This conformational feature has been associated with increased biological activity of these hormones. We demonstrate, however, that two calcitonin analogs, [Gly8,Ala16]-des-Leu19 salmon calcitonin and des-1-amino-[Ala1,7,Gly8]-des-Leu19 salmon calcitonin have minimal interactions with phospholipids. Neither of these peptides acquire any increased helical content in the presence of dimyristoylphosphatidylglycerol and these peptides have only weak effects in altering the phase transition properties of this lipid. Therefore, although the presence of a phospholipid-induced amphipathic helical sequence may enhance the biological activity, it is not required for activity.