The relative susceptibility of 4 tropical maize pests, Spodoptera frugiperda (J. E. Smith),Diatraea grandiosella Dyar, D. saccharalis (F.), and Helicoverpa zea (Boddie), to the lepidopteran-specific CryI-type proteins produced by B. thuringiensis is presented. The toxin with the highest potency against H. zea larvae was the CryIAc toxin. S. frugiperda larvae were susceptible to CryID and CryIF toxins. The CryIB toxin showed to be highly toxic against D. grandiosella and D. saccharalis. This information will establish a basis for selecting B. Thuringiensis strains producing the appropriate CryI proteins to be used for the biological control of these tropical pests.