Technical Abstract: Surveys of free-ranging deer in Michigan have identified the first known epidemic of tuberculosis in white-tailed deer. Information is lacking on the transmissibility of Mycobacterium bovis among deer. To determine the efficiency and routes of transmission between deer we exposed non-inoculated deer to deer that had been experimentally inoculated by intratonsilar instillation of 2x10*8 CFU of M. bovis. Two in-contact deer were penned with 2 experimentally inoculated deer; each pen having a single source of water, hay, and pelleted feed. Sixty-nine days after introduction, all in-contact deer manifested delayed type hypersensitivity (DTH) reactions to M. bovis purified protein derivative (PPD). All experimentally inoculated deer were removed one-hundred-twenty days after inoculation. One-hundred-fifty-nine days after introduction, 4 new non-inoculated deer were housed with the remaining original in-contact deer such that 2 new in-contact deer were penned with 2 original in-contact deer. One-hundred days after introduction, all new in-contact deer demonstrated DTH to M. bovis PPD. At 180 days after introduction of new in-contact deer, deer were euthanized and examined. All in-contact exposed deer developed tuberculosis. Lesions were most common in the lung and pulmonary lymph nodes. Experimentally inoculated deer shed M. bovis in nasal secretions, saliva, feces, and urine. In-contact infected deer also shed M. bovis in nasal secretions and saliva. Hay and pelleted feed contained M. bovis at multiple times during the experiment. Tuberculous deer efficiently transmit M. bovis to other deer in close contact. Lesion distribution suggests aerosol transmission, however, contamination of shared feed also must be considered.