A technique is described for determining the antimicrobial susceptibility of Mycoplasma gallisepticum, using the Sensititre broth microdilution system. Fourteen M. gallisepticum field isolates and one reference isolate (R-strain) were tested in duplicate against seven antimicrobials. Isolates were susceptible to oxytetracycline, furaltadone, and lincomycin/spectinomycin, but not to amoxycillin and apramycin. Susceptibility to erythromycin and tylosin varied. These data are in agreement with those reported by other workers using more traditional methods, but this adaptation of the broth microdilution technique eliminates any variation attributable to the time-consuming preparation of antimicrobial dilutions associated with these methods.