The article reports on the use of Kirby-Bauer tests to analyze the antibiotic resistance of 224 isolates of Riemerella anatipestifer isolated between 1998 and 2005. Resistance to ampicillin, ceftazidime, aztreonam, cefazolin, cefepime, cefuroxime, oxacillin, penicillin G, rifampin and trimethoprim/sulfamethoxazole was found in 50 percent of the isolates analyzed. The therapeutic efficacy of the antibiotics against lethal R. anatipestifer infection in ducks in vivo were also examined. An antibiotic treatment approach for veterinarians attending flocks of ducks was extrapolated according to the data. The identification of effective antibacterial treatments is facilitated and the irresponsible use of antibiotics is potentially decreased.