Seventy-four cultures of Pasteurella multocida representing all four capsular types, A, B, D, and C, from various animal species and diseases were examined for the production of hyaluronidase by two procedures. In one, hyaluronidase production was determined by the depolymerization of streptococcal capsular hyaluronic acid, and in the other, production was determined by degradation of sodium hyaluronidate in a solid culture medium. Hyaluronidase production was only demonstrated in the 13 type B cultures that had been recovered from cases of hemorrhagic septicemia.