Bacillus thuringiensis subsp. galleriae forms spontaneous asporogenic, crystalliferous variants (Spo(-)Cry(+)) especially under continuous culture conditions. These variants gradually replace the wild-type strain (Spo(+)Cry(+)) entirely in the culture. Spo(-)Cry(+) variants form amorphous insecticidal crystalline inclusion bodies, that are difficult to solubilize and less toxic to the caterpillars of Bombyx mori. However, the defective inclusion bodies and their trypsin-digested peptides exhibited similar antigenic profiles to that of native crystals in Western blot analysis. Apparently a block in the formation of spores does not affect the synthesis of the constitutive peptides of the crystals but may interfere with the proper assembly of the crystalline endotoxin.