The taxonomic position of an actinomycete strain isolated from Korean soil was examined by a polyphasic approach. The isolate, designated IMSNU-1, was clearly assigned to the genus Streptomyces on the basis of morphological and chemotaxonomic data. The test strain was the subject of a probabilistic identification study using the identification matrices generated by Langham et al. (J. Gen. Microbiol. 135:121-133, 1989) and found to be marginally close to clusters 19 and 39. An almost complete 16S rRNA gene (rDNA) sequence was obtained for the test strain and compared with those of representative streptomycetes. 16S rDNA sequence data not only support the strain's membership in the genus Streptomyces but also provide strong evidence that our isolate is genealogically distant from representatives of clusters 19 and 39, forming a separate phyletic line in a clade encompassed by streptomycetes. It is therefore proposed from the polyphasic evidence that strain IMSNU-1 be classified in the genus Streptomyces as Streptomyces seoulensis sp. nov.