Bovine Leukemia Virus (BLV) infection is common in the world. This infection has also been in Turkey since 1942. Between the years of 1991 and 1994, 941 cattle over the age of six months were investigated using commercially prepared kits for anti-BLV antibodies by ELISA in the Bursa Region of Turkey. Five hundred-fifty blood samples were obtained from cattle of 133 stables in 51 villages found in 10 counties, and also 391 blood samples from the cattle in Bursa abattoir. BLV anti-gp 51 antibodies were determined in 80 (8.50%) out of 941 cattle. BLV antibodies were also determined in 68 cattle (12.36%) in the 10 counties and it was observed that 13 (19.11%) of them had persistent lymphocytosis (1.47%) of them was in lymphosarcoma form. The highest infection rates in Karacabey (25.00%) and Nilufer (18.80%) counties were because of the two semi-intensive farms found there. The results also revealed that BLV infection was most common in animals between five and six years old. For control of transmission of BLV, iatrogenic transmission should be prevented; for this aim, different needles and other tools should be used for each animal. The cattle with persistent lymphocytosis must be particularly eradicated as soon as possible. An eradication programme should be implemented in Turkey as in other countries.