Abstract: A prospective longitudinal study was performed of brucellosis’ monthly incidence during a period of six years, in a bovine dairy farm revaccinated with RB51 and endemic presentation of brucellosis, monthly serologies were done to the total amount of cows (average of 340). Prevalence at the beginning of the study was 15.3%. All negative animals were vaccinated with RB51 reduced doses and revaccinated. Card Test (CT) was executed and the positive sera were tested by rivanol. Sampling on day 150 showed incidence of 21%. During the first 360 days of the study, the cows that were positive to serology were not eliminated. During the period between 390 to 960 days, positive animals were eliminated, obtaining with this type of handling, incidences below 2%. Between days 990 to 1830 we returned to the criteria of not eliminating positives and therefore monthly incidences were 2%. From day 1830 on, all seropositive cows were eliminated with incidences during day 2160 and 2190, last day of our study, of 0.5 and 0.25%, respectively. The conclusion that we arrived at is that to have an efficient control of brucellosis, a vaccination program appropriate for epidemiological conditions of brucellosis in the region is required.