The anticancer properties and mechanism of action of a hybrid peptide -P18 were investigated. It had significant cytotoxic activity against human melanoma cells and low toxicity to normal NIH-3T3 cells. It also induced cell death via necrosis rather than classical apoptosis. The peptide targets the cells membrane, causing a sustained depolarization of transmembrane potential resulting in the cells swelling and bursting, thereby triggering cytolysis. P18 peptide initially binds to the melanoma cell membrane via electrostatic interaction, causing the cell membrane to rupture. The effect may be mediated by the amphiphilic alpha-helical structure of P18 peptide, coupled with changes in ion channels and an increase in plasma membrane permeability that eventually leads to melanoma cell death.