An analysis of the ribosomal AT-L30 proteins from 42 strains of 35 species belonging to the genera Streptomyces, Streptoverticillium, and Kitasatosporia and related genera revealed that all of the members of the genera Streptoverticillium and Kitasatosporia examined had the same sequence as Streptomyces exfoliatus or a highly homologous sequence and exhibited high levels of relatedness to Streptomyces lavendulae. These results strongly support the previous suggestion of Witt and Stackebrandt (D. Witt and E. Stackebrandt, Syst. Appl. Microbiol. 13:361-371, 1990) and Wellington ct al. (E. M. H. Wellington, E. Stackebrandt, D. Sanders, J. Wolstrup, and N. O. G. Jorgensen, Int. J. Syst. Bacteriol. 42:156-160, 1992) that the genera Streptoverticillium and Kitastaosporia should be united with the genus Streptomyces on the basis of 16S rRNA data.