Genomic DNA of the entomopathogenic bacterium Bacillus thuringiensis was analyzed by the genomic fingerprinting technique. The biotin-labeled single-stranded DNA of the phage M13 was used as a marker of hypervariable sequences. A procedure for analyzing the differentiation among various Bacillus thuringiensis strains was developed. Characteristic patterns of fingerprints were obtained for several strains, the main representatives of subspecies that are most frequently used in the manufacture of bacterial insecticides, such as subsp. thuringiensis, subsp. kurstaki, and subsp. galleriae. Because no essential differences were revealed in band patterns upon comparing fingerprints of crystal-producing bacterial strains with those of acrystallic mutants, it was assumed that the loss of crystal-producing ability in the insect pathogen Bacillus thuringiensis is not connected with significant rearrangement of its genome.