Cecropins and other related peptides are induced in insects and composed of over 30 amino acids with strong antibacterial activity,which is due to formation of large pores in bacterial cell membranes by their specific secondary structure. Analogs of these peptides which do no harm to eukaryotic cell membrances in lethal concentrations for bacteria have been found in mammalian cells. Owing to their broad antibacterial activity,cecropins and other peptides have brought attention of plant pathologists and medical scientists and been applied to the research of medicine and plant antibacterial infection.