The aim of the present study was to determine the tolerance and efficacy of human brucellosis vaccine as well as the tolerance and sensitivity of the intradermal reaction test for brucellosis. A total of 1,121 subjects initially consented to participate in the study. Following clinical examination, 762 were tested with the intradermal reaction test (IDR Test, Pasteur Merieux, France), of whom 576 with no previous or current brucellosis infection were accepted for vaccination. Two hundred seventy-one were vaccinated with brucellosis vaccine and 305 with tetanus vaccine, the latter group serving as a comparative control group. The vaccinated persons were monitored monthly for at least nine months. Although brucellosis vaccine caused some unpleasant side effects in about one-fourth of the vaccinated persons, it appears safe for large-scale use in prevention programs. In addition, the results indicate that the intradermal reaction test is safe and sensitive for large-scale use in prevention programs. The test was positive in 28 of 30 individuals with previous infection, representing a sensitivity of 93.33%.