Almost complete 16S rRNA sequences from seven Thermomonospora strains, Thermomonospora curvata, Thermomonospora formosensis, Thermomonospora fusca, Thermomonospora mesophila, Thermomonospora chromogena, Thermomonospora alba and Thermomonospora mesouviformis (a synonym of Thermomonospora alba) were determined and subjected to phylogenetic analysis together with the sequences from all the representative members of the suborder Streptosporangineae. On the basis of phylogenetic, chemotaxonomic and phenotypic evidence, the transfer is proposed of Thermomonospora formosensis to the genus Actinomadura as Actinomadura formosensis comb. nov., Thermomonospora mesophila to the genus Microbispora as Microbispora mesophila comb. nov., and Thermomonospora fusca and Thermomonospora alba to a new genus, Thermobifida gen. nov., which belongs to the family Nocardiopsaceae, as Thermobifida fusca comb. nov. and Thermobifida alba comb. nov. Thermobifida alba is designated the type species of the genus. The transfer is also proposed of all species of the Microtetraspora pusilla group, which were transferred from Actinomadura, to a new genus, Nonomuria gen. nov., as Nonomuria africana comb. nov., Nonomuria angiospora comb. nov., Nonomuria fastidiosa comb. nov., Nonomuria ferruginea comb. nov., Nonomuria flexuosa comb. nov., Nonomuria helvata comb. nov., Nonomuria polychroma comb. nov., Nonomuria pusilla comb. nov., Nonomuria recticatena comb. nov., Nonomuria roseola comb. nov., Nonomuria roseoviolacea comb. nov., Nonomuria rubra comb. nov., Nonomuria salmonea comb. nov., Nonomuria spiralis comb. nov. and Nonomuria turkmeniaca comb. nov. Nonomuria pusilla is designated the type species of the genus.