Two coryneform bacteria isolated from human clinical specimens were characterized by phenotypic and molecular taxonomic methods. Chemotaxonomic investigations revealed the presence of cell-wall chemotype IV and short-chain mycolic acids consistent with the genus Corynebacterium sensu stricto. Comparative 16S rRNA gene sequence analysis showed that the two strains are genealogically highly related (99.8% sequence similarity) and constitute a new subline within the genus Corynebacterium, with Corynebacterium minutissimum as their nearest phylogenetic neighbours (98.8% sequence similarity). However, DNA-DNA hybridization experiments demonstrated unambiguously that the isolates are genealogically distinct from Corynebacterium minutissimum (42% homology). Biochemical testing indicated that the two isolates were hardly differentiated from Corynebacterium minutissimum. Based on both phenotypic and phylogenetic evidence it is proposed that these isolates be classified as a new species, Corynebacterium aurimucosum sp. nov. The type strain of Corynebacterium aurimucosum is represented by strain IMMIB D-1488T (= DSM 44532T = NRRL B-24143T).