Amphiphilic oligopeptides containing a hydrophobic alpha-helical amino acid sequence were prepared and studied with respect to their ability to be integrated into the lipid double layer of phospholipid liposomes, The incorporation of the amphiphilic peptides was determined from the disturbance of the characteristic ripple phase of liposomes by means of freeze-fracture electron microscopy, from the decrease in mobility of fluorophoric groups by means of fluorescence anisotropy decay measurements, and from the formation of porous areas in black lipid membranes.