The taxonomic position of unidentified group 6 of Bacillus circulans as described by Nakamura and Swezey (L.K. Nakamura and J. Swezey, Int. J. Syst. Bacteriol. 33:46-52, 1983) was determined, and the taxonomy of Paenibacillus amylolyticus was reexamined. The results of PCR amplification of a 16S rRNA gene fragment with a specific primer and comparative analysis of 16S rRNA gene sequences warranted placing the two taxa in the genus Paenibacillus. The levels of DNA reassociation among the strains revealed four groups (designated groups I, II, III, and 6), each with a high level of intragroup relatedness (> 72%). Clustering based on phenotypic characteristics correlated well with DNA relatedness grouping. P. amylolyticus strains were scattered in groups I, II, and III. Strains labeled the type strain of P. amylolyticus from different culture collections appeared in groups I and III. Strains found in group I were identified as P. amylolyticus sensu stricto, and the one strain found in group III was identified as Paenibacillus lautus. Group 6 encompassed strains formerly assigned to B. circulans group 6, and group II contained other strains identified as P. amylolyticus. Groups 6 and II were phenotypically and genetically distinct taxa that were distinguishable from the previously described species. These findings showed that groups 6 and II were new species, for which we propose the names Paenibacillus illinoisensis and Paenibacillus chibensis, respectively.