Brucellosis is a highly pleomorphic zoonotic infection caused by one of the following four species of gram-negative facultative intra-cellular coccobacilli: Brucella melitensis, B. abortus, B. suis, or B. canis. The disease is a worldwide public health problem and a significant cause of economic losses in domestic livestock. Although largely eradicated in most industrialized countries, in the United States there has been an upsurge of B. melitensis cases associated with the ingestion of unpasteurized goat's milk or goat's milk cheese from Mexico. Brucellosis can be either insidious or abrupt in onset and can affect virtually every organ system; skeletal involvement (spondylitis, arthritis) is the most frequent metastatic complication. Cases are diagnosed either by isolation of the bacterium (usually from blood) or by serologic testing. Treatment of brucellosis requires the administration of two antimicrobial agents. Doxycycline plus streptomycin or rifampin or trimethoprim-sulfamethoxazole plus rifampin appear to be the most effective regimens.