The aims of this study were to determine differences with respect to immunogenic potency in the antigenic profiles of nine Lactococcus garvieae strains from Turkey, Spain, and England, to develop a bacterin, and to examine the immunological response of rainbow trout to the bacterin. The strains had identical Western blot patterns with 30, 37, 40, 46, 52, and 66 kDA mw protein bands. After culturing the bacteria, proteins were separated by SDS-PAGE and transferred to Immobilon membranes. The membranes were incubated with hyperimmune rabbit sera obtained by immunizing a rabbit against L. garvieae. One group of 50 fish was immunized with formalin-killed bacterin prepared from the most immunogenic strain of L. garvieae. A second group of 50 fish served as an unimmunized control. Four weeks after vaccination, both groups were challenged intraperitoneally with a homologous strain. The protection rate of the bacterin was judged by the relative percent survival (RPS) of the groups. A significantly high level of protection was achieved in the vaccinated group (88.8% RPS).