This study was carried out during the period 2004- 2006 to follow up the pattern of occurrence of brucellosis in a farm of dairy Friesian cattle (in Damitta Governorate, Egypt) from which B. melitensis biotype 3 had been previously isolated and the farm had been put under quarantine of veterinary authorities through the period 2001-2003. All animals inside the farm including 451 cows, 49 pregnant heifers and 6 bulls were serologically tested using RBT, TAT and Riv. test at three weeks intervals for two years. The results showed that the prevalence of brucellosis ranged from 0.95% to 9.79%. The incidence (every 6 months) of brucellosis was always higher in pregnant heifers (8.1%, 31.8% and 5.2%) than in mature cows (1.8%, 9.3% and 2.5%) in the first, second and third examination respectively. Concerning bulls, only one (16.6%) was found positive at the beginning of our study. None of the other 5 bulls seroconverted during period of the study. The study also included 3 dogs and 70 rats that were trapped in the farm where all the dogs and 10 (14.28%) of the rats were positive for brucellosis by the same tests.Besides, 55 high milk producing positive cows that had been isolated in an independent place and separately milked for more than      2 years were annually tested using RBT, TAT and CFT to follow up the changes in their serological status. The results of annual serological examination of these cows revealed that there was a continuous decline in the percentage of positive animals where by the end of the study; 22 (45.5 %) out of the 55 positive cows reverted to the negative serological status. It was concluded that, despite efforts, Failure to control infection for this long time was thought to be due to the bad hygienic conditions, presence of infected dogs and rats, presence latently infected heifers and the use of RB51 vaccine that does not confer complete protection against B. melitensis infection.