Two strains of xylanase-producing bacteria, S3-4A(T) and MX2-3(T), isolated from soils in Thailand, were characterized on the basis of their phenotypic and chemotaxonomic characteristics, DNA-DNA relatedness and 16S rRNA gene sequences. The novel strains were Gram-positive, facultatively anaerobic, spore-forming, rod-shaped bacteria. They contained meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C contents of strains S3-4A(T) and MX2-3(T) were 52.7 and 52.9 mol%, respectively. The major isoprenoid quinone was MK-7. The dominant cellular fatty acids were anteiso-C(15 : 0) and iso-C(16 : 0). Phylogenetic analyses using 16S rRNA gene sequences showed that both novel strains were affiliated to the genus Paenibacillus. Strains S3-4A(T) and MX2-3(T) were closely related to Paenibacillus agaridevorans DSM 1355(T) with 97 % and 97.3 % gene sequence similarities, respectively. The DNA-DNA relatedness between strains S3-4A(T), MX2-3(T) and P. agaridevorans DSM 1355(T) was low (6.0-30.3 %). The novel strains could be clearly distinguished from P. agaridevorans DSM 1355(T) by physiological and biochemical characteristics. Therefore, these two strains represent novel species of the genus Paenibacillus, for which the names Paenibacillus thailandensis sp. nov. (type strain S3-4A(T)=KCTC 13043(T)=PCU 275(T)=TISTR 1827(T)) and Paenibacillus nanensis sp. nov. (type strain MX2-3(T)=KCTC 13044(T)=PCU 276(T)=TISTR 1828(T)) are proposed.