The suitability of tDNA-PCR fingerprinting to identify species of the genus Bacillus was tested on 75 strains. Strains belonging to the same species or the same phylogenetic cluster were correctly grouped. Among B. stearothermophilus strains, different pattern types were found. This could be due to the unclear taxonomic situation of these strains, rather than to a failure of the tDNA-PCR. Single strand conformation polymorphism (SSCP) of the PCR products allowed species discrimination within the 'B. subtilis group', but not within the 'B. cereus group'. The tDNA-PCR, alone or coupled with SSCP analysis, is useful to address Bacillus species identification, particularly for those species which are not phylogenetically tightly clustered.