Disclosed is a cell lytic polypeptide that has a region capable of forming an amphipathic alpha helix and a net charge of +12 or more, or that contains 3 regions, each capable of forming an amphipathic alpha helix. A nucleic acid encoding the polypeptide is also disclosed. Also within the scope of this invention are a pharmaceutical composition containing the polypeptide or nucleic acid and a pharmaceutically acceptable carrier, and a method for treating a cellular proliferative disorder.