Epidemiological analysis has indicated that rat and reindeer brucellosis foci are of definite value in Siberia and the Far East in the liquidation of brucellosis ones. Foci of cattle and reindeer have been first established, evidence has been provided for the epidemiological significance of fifth-biological variant B. ovis and B. suis, as well as the ecological confinement of peculiar B. rangiferi cultures to the brucellosis foci in the Arctic. To plan antibrucellosis efforts, it is necessary to take into account the incidence of human infection, as well as the insidious circulation of the bacillus in the stock farms.