The in-vitro sensitivity of 16 Australian isolates of Bordetella avium and 15 isolates of B avium-like organism to 11 antimicrobial agents or combinations of agents was determined using a microtitre plate system to establish minimal inhibitory concentrations. All the B avium isolates were sensitive to ampicillin but resistant to erythromycin, lincomycin, spectinomycin, sulphamethoxazole, trimethoprim, and lincomycin + spectinomycin. Most of the B avium isolates were sensitive to tetracycline and resistant to streptomycin and sulphadiazine. All the B avium-like isolates were resistant to ampicillin, erythromycin, lincomycin, spectinomycin, streptomycin, tetracycline, trimethoprim, and lincomycin+spectinomycin. Most B avium-like isolates were sensitive to sulphadiazine, sulphamethoxazole and trimethoprim-sulphamethoxazole.