Brucellosis is a zoonosis caused by Brucella species. B. melitensis, B. suis, B. abortus and B. canis can infect humans. Recently, as the cases of bovine brucellosis have increased every year in Korea, the cases of human brucellosis have also increased among livestock workers and veterinarians in rural areas, since the first human case was reported in 2003. Because clinical manifestations of the disease are nonspecific and may be very atypical, clinicians and laboratory persons need to be active in using diagnostic tools including polymerase chain reaction in addition to the ordinary culture and serologic tests, and taking an appropriate measure to prevent intralaboratory infection. We report herein our experience in three human brucellosis cases diagnosed by cultures, serologic tests and gene detection. (Korean J Clin Microbiol 2007;10:154-159)