The synthesis of three cyclic peptides related to an active sequence of Laminin is described. These molecules have no, one, or two stearoyl residues linked to the amino terminal end of the sequence. The physicochemical properties of these peptides as well as their interactions with dipalmitoylphosphatidylcholine molecules ordered in mono- and bilayers are described. Properties based on aqueous solutions of peptides show maximum activity for the analogue with one stearoyl residue. But properties measured from organic solutions of peptides (compression isotherms), as well as those in water but at high temperatures, gave as the most surface active the distearoyl derivative. This behavior is interpreted as a strong tendency of this highly hydrophobic molecule to form aggregates (probably micelles), very stable in aqueous media. Thus, the monostearoyl-substituted peptide seems to be the most adequate for efficient insertion into mono- and bilayers.