DNA relatedness experiments were performed with 38 clinical isolates and 13 reference strains of coryneform taxa exhibiting a lipid requirement for optimal growth. Forty-five of these strains split into five genomic groups at the species level, whereas six other strains remained unclustered. Genomospecies I1 fits Corynebacterium accolens, but the other genomospecies were not genetically related to any of the defined Corynebucterium species. Phylogenetic analyses of genes coding for small-subunit rRNA sequences revealed that two genomospecies (I and 111) and C. uccolens form a tight cluster within the robust branch that groups all Corynebacteriun species presently sequenced. Reference strains of biotypes C-1, C-2, and C-3 of "Corynebacterium pseudogenitulium" were found to fall into genomospecies I, as well as "Corynebacterium tuberculostearicum," Centers for Disease Control and Prevention (CDC) coryneform group G-1, and CDC coryneform group 6 -2 reference strains. Biochemical tests allowed differentiation between genomospecies except between genomospecies N and V and between six unclustered strains and genomospecies I. We propose a new classification for these lipid-requiring diphtheroids within the genus Corynebucterium with the delineation of some CDC coryneform group G-1 strains (genomospecies 111) as a new species for which the name Corynebacterium mucginleyi is proposed. The type strain is strain JCL-2 (CIP 104099), isolated from a human corneal ulcer.