Insect pests are a major cause of damage to the world's commercially important agricultural crops. Current strategies aimed at reducing crop losses rely primarily on chemical pesticides. Alternatively transgenic crops with intrinsic pest resistance offer a promising alternative and continue to be developed. The first generation of insect-resistant transgenic plants are based on insecticidal proteins from Bacillus thuringiensis (Bt). A second generation of insect-resistant plants under development include both Bt and non-Bt proteins with novel modes of action and different spectra of activity against insect pests.