The M-9 and Minnesota (MN) avirulent Pasteurella multocida vaccines were evaluated and compared with the Clemson University (CU) vaccine, which had been shown to be highly effective in preventing fowl cholera in turkeys. Neither the M-9 nor the MN vaccine given in the drinking water was as effective as the CU vaccine in protecting turkeys against challenge with virulent P. multocida. When grown in brain-heart infusion (BHI) agar as recommended, the M-9 was not as efficacious as when it was grown in BHI broth. The M-9 was as effective as the CU vaccine only when grown in BHI broth and given at 10 times the standard dosage. Injection of the M-9 vaccine into the air spaces of the head at a site near the caudal rim of the ear after one vaccination in the drinking water was not as effective for hyperimmunizing potential breeders as was the CU vaccine injected at the same site. A microtiter agglutination test demonstrated a significant (P less than 0.05) correlation between the level of anti-P. multocida antibody found 1 week after vaccination and survival after challenge with virulent P. multocida.