In a 9 month-old infant admitted to hospital for a fever with chilles, anaerobic blood cultures isolated Fusobacterium necrophorum. On the 5th day of intravenous treatment with amoxicillin and metronidazole clinical signs of mastoiditis, the likely source of the sepsis, became apparent. Septicemias with Fusobacterium necrophorum are usually observed in teenagers and young adults during an acute bout of tonsilitis. This type of infection is exceptional in infants and requires a careful search for a primary focus in facial cavities and in the base of the skull.