Five cases of laboratory-acquired infection with Brucella melitensis are reported. This pathogen is highly contagious when handled in the laboratory. Clinicians should alert technologists when brucellosis is suspected so that specimens are handled under the most stringent safety measures. Serological surveys and instructions of laboratory workers regarding the clinical diversity of the disease are helpful for early recognition of secondary cases. On the other hand, clinicians should consider brucellosis in medical laboratory workers with unexplained signs and symptoms.