Dependence of the concentration of peptide antibiotics on the lysis of liposomes of different compositions is presented in this study. Here, we clearly demonstrate that cecropin B and its analogues can lyse anionic liposomes immobilized on a biosensor chip. Surface plasmon resonance measurements showed that, for two peptides, lysis was only induced at low peptide concentrations and, at higher concentrations, the peptides bound to the liposomes without lysing them. The concentration-dependent mechanism of peptide-lipid interactions revealed here is relevant to the action of cationic peptides on the anionic membranes of bacteria and neoplastic cells. Use of the technique described here will provide a new direction to assess the action and efficacy of antibacterial peptides, antibiotics, and anticancer agents.