IN-VITRO: Sensitivity tests of pasteurella anatipestifer (PA) serotypes 2, 3 and 5 to 24 antimicrobial agents proved that all tested serotypes were highly sensitive to Flumequine and Oxalinic acid. Flumequine was tested for therapeutic efficacy against PA serotype "3" in ducklings. The efficacy of the drug was evaluated according to clinical signs, survival rates and frequency of isolation from different organs follow ing challenge. IN-VIVO: Flumequine used either before, during or after experimental infection significantly prevented the appearance of both clinical signs and lesions of the disease and reduced the rate of reisolation of PA when compared with untreated birds. Lactose gave similar results like flumequine when given in drinking water at a rate of 2.5%.