CryIIIB2, an insecticidal protein from Bacillus thuringiensis has been crystallized from 0.6 M NaBr and HEPES buffer at pH 7.0 and X-ray diffraction data collected on a native crystal to 2.4 A. The insecticidal protein was obtained from a Bacillus thuringiensis (Bt) strain EG7231. Crystals of the endotoxin are orthorhombic, space group C2221, with unit cell dimensions of a = 122.44, b = 131.81, and c = 105.37 A. A unit cell contains one molecule of the 67,000 Da endotoxin per asymmetric unit.