A DNA-DNA hybridization survey was performed on 13 Streptomyces species and two subspecies, dispersed over five genotypically defined clusters as delineated by Lanoot et al. [Syst Appl Microbiol 27 (2004), 84-92]. Within each of the latter clusters, strains shared DNA-DNA relatedness values above 70 %. On the basis of published recommendations, the following eight Streptomyces species with validly published names are considered as later synonyms: Streptomyces nigrifaciens as a synonym of Streptomyces flavovirens; Streptomyces citreofluorescens, Streptomyces chrysomallus subsp. chrysomallus and Streptomyces fluorescens as synonyms of Streptomyces anulatus; Streptomyces chibaensis as a synonym of Streptomyces corchorusii; Streptomyces flaviscleroticus as a synonym of Streptomyces minutiscleroticus; and Streptomyces lipmanii, Streptomyces griseus subsp. alpha, Streptomyces griseus subsp. cretosus and Streptomyces willmorei as synonyms of Streptomyces microflavus. Emended descriptions are proposed.