In a study conducted from January to August 2000, elk (Cervus elaphus) were vaccinated with Brucella abortus strain RB51 (SRB51, n=6) or injected with 0.15 M NaCl solution (n=3) at approximately 6 mo of age. Beginning at 2 wk and continuing to 25 wk after vaccination, SRB51-vaccinated elk had greater antibody responses (P<0.05) to SRB51 when compared to nonvaccinated elk. Peripheral blood mononuclear cells (PBMC) from SRB51-vaccinated elk had greater (P<0.05) proliferative responses to SRB51 at 18 wk after vaccination when compared to responses of nonvaccinated elk. Strain RB51 was recovered from blood samples of all vaccinates at 2 wk, and three of six vaccinates at 4 wk after vaccination. The SRB51 vaccine strain was recovered from the superficial cervical lymph node of all vaccinates sampled at 6 wk after vaccination, but not from lymph node samples obtained from vaccinates at 12 or 18 wk after vaccination. At 34 wk after vaccination, SRB51 was recovered from the bronchial lymph node of one of five vaccinates but not from other tissues. Strain RB51 was not recovered at any time from samples obtained from nonvaccinated elk. This study suggests that following vaccination with SRB51, elk remain bacteremic for a prolonged period of time, rapidly develop high antibody titers, and are slower to develop detectable proliferative responses in PBMC when compared to responses of cattle or bison (Bison bison).