Detection of Arcanobacterium haemolyticum is based upon typical beta-hemolysis and colony morphology, but it may go undetected if only conventional sheep blood agar media for detection of beta-hemolytic streptococci are used. The influence of different culture media, atmospheres, and times of incubation for the recognition of colonies of 47 isolates of A. haemolyticum was studied. After 48 h of incubation, trypticase soy agar with 5% horse blood in 5% CO(2) was the best medium.