Lectins are carbohydrate-binding glycoproteins found in many plant species. They possess a broad range of antimicrobial properties and also are toxic to some insect species. Their toxicity to insects relates to their ability to bind to their midgut and impair the absorption of nutrients thereby inhibiting their growth. F2 plants were grown from seed of individual regenerated plants of cotton (Coker-312) transformed with lectin genes from various sources. After the plants reached the four-leaf stage, leaf tissues were fed to neonate worms (Heliothis virescens) for six days. On the seventh day their weights were recorded. Controls were plants that were transformed with plasmid pMON 893 without the lectin gene. Transformed plants, depending on the transformation event, inhibited worm growth to varying degrees compared with the controls.