Vaccination of ducks against fowl cholera was done using avirulant CU strain via drinking water at 4-' weeks of age under laboratory and field conditions. Challenge of the vaccinated ducks by virulent Pasteurella multocida (PM) serotype 1 Prooved that the vaccine produc ed high protection rate of 85%. Serial five blind passages of the vaccin al strain in susceptible ducks did not result in increased virulence of the strain and prooved that the vaccine was safe for ducks. Efficacy of the vaccine under field conditions was prooved according to the following parameters, livability, body weight and protection after chal lenge.