Abstract: Cecropins are found in divergent sources. All cecropins identified are highly potent antimicrobial peptides in vitro. Several are found effective against a number of phytopathogens in vivo.With the deeper understanding of cecropins and their functional mechanism, great progress was made in plant genetic transformation with genes encoding natural and chemically modified cecropins. Problems associated with functional expression of cecropins in transgenic plant were also discussed.