Entomopathogenic nematodes are being used for insect control. We purified a toxin secreted by the insect-pathogenic bacterium, Xenorhadbus nematophilus, which lives in the gut of entomopathogenic nematodes. Culture broth of X. nematophilus was separated by centrifugation and concentrated by ultration. The concentrated culture broth was applied to a DEAE Sephadex A-50 column, and proteins were eluted stepwise with increasing concentrations of KCI. Fractions column. The molecty weight of purified toxin was39 kDa on SDS-PAGE, and Fourier tranformed infrared (FTIR) spectroscopy indicated that this toxin could be a new protein exhiting the charactristics of C=O stretching peak near 1650cm-1.