Tuberculin positive cattle without gross tubercle lesions should be confirmed by the bacteriological examination to determine the state of the infection. To overcome the time-consuming and laborious identification by culture and biochemical tests, polymerase chain reaction (PCR) has been used to identify Mycobacterium bovis. Due to various lipids in the cell wall of Mycobacterium spp, novel methods of DNA extraction from Mycobacterium spp have been developed. In this study, a newly developed guanidium isothiocyanate/silica DNA extraction method was directly applied to specimens from the tuberculin positive cattle. DNAs were directly extracted from the lymph nodes and the major polymorphic tandem repeat (MPTR) and mycobacterial protein of BCG 70 (MPB70) were amplified using PCR. The DNA extraction method using guanidium isothiocyanate/silica was efficient and safe, and the MPTR and MPB70 primers were specific to M bovis. Therefore, MPTR and MPB70 PCRs will be useful for the detection of M bovis in the lymph node from skin-test positive cattle.