This study was conducted to detect the Y-specific DNA in the blood of the female calf in bovine heterosexual production. Genomic DNAs of the freemartin were isolated from the blood and amplified with Y-chromosome specific DNA primer(l4lbp). In order to estimate the lower limit for the detection of XY cells, blood from a hull was diluted in cow blood to 0.01%. DNA sequencing on the PCR products was shown the same sequences as Y chromosome DNA of the normal cows. The Y specific DNA hand by PCR was detected all blood of female calf suspected to have bovine freemar tin syndrom and the karyotyping with freemartin blood was identified as XX / XY chimerism. Therefore, the PGR methods used in this study was very useful technique for the detection of freemartin in Ranwoo and Holstein.