'Corynebacterium haemolyticum' (MacLean, Liebow & Rosenberg) differs to such an extent from the type species of Corynebacterium, C. diphtheriae (Lehmann & Neumann), that it should be removed from this genus. Chemical and numerical phenetic data indicate that 'C. haemolyticum' is a distinct taxon worthy of generic status. A new genus, Arcanobacterium, is described for the species A. haemolyticum (MacLean, Liebow & Rosenberg) nov.rev., comb.nov. The genus is tentatively placed within the 'coryneform group of bacteria'. The type species of the genus is Arcanobacterium haemolyticum and the type strain is ATCC 9345.