The genus Saccharothrix is phylogenetically heterogeneous on the basis of analysis of almost complete 16S rDNA sequences. An evaluation of chemotaxonomic, morphological and physiological properties in the light of the molecular phylogeny data revealed that several species are misclassified. Saccharothrix aerocolonigenes NRRL B-3298T and Saccharothrix flava NRRL B-16131T constitute a lineage distinct from Saccharothrix and separate from Lentzea. The genus Lechevalieria gen. nov. is proposed for these species. Lechevalieria aerocolonigenes comb. nov. is the type species and S. flava is transferred as Lechevalieria flava comb. nov. Although Lentzea albidocapillata, the type species of the genus Lentzea, was transferred recently to the genus Saccharothrix, the revival of Lentzea is clearly supported by molecular phylogenetic and chemotaxonomic data. The description of the revived genus is emended to include galactose, mannose and traces of ribose as diagnostic whole-cell sugars and MK-9(H4) as the principal menaquinone and elimination of tuberculostearic acid as a diagnostic component in the fatty acid profile. Saccharothrix waywayandensis NRRL B-16159T, S. aerocolonigenes NRRL B-16137 and 'Asiosporangium albidum' IFO 16102 are members of the amended genus Lentzea on the basis of phylogenetic and chemotaxonomic properties. S. waywayandensis is transferred to Lentzea as Lentzea waywayandensis comb. nov., while the new species Lentzea californiensis sp. nov. and Lentzea albida sp. nov. are described for S. aerocolonigenes NRRL B-16137 and 'A. albidum' IFO 16102, respectively. Nucleotide signatures in the 16S rDNA sequences are defined that are diagnostic for the genera Lechevalieria, Lentzea and Saccharothrix.