In this paper, four diagnostic techniques were compared in terms of their ability to detect BVD virus in buffy coats frozen for more than one year. The samples were selected according to their initial test results. Forty-five BVDV positive and 15 BVDV negative buffy coats were used. The techniques used were the virus isolation-immunoperoxidase test (IPX), immunoperoxidase monolayer assay (IPMA), indirect immunoperoxidase monolayer assay (IIPMA) and reverse transcription-polymerase chain reaction (RT-PCR). All BVDV negative samples from previous studies were also negative on the tests used in this study. Out of 45 BVDV-positive samples, 42 (93.3%) were found to be positive with RT-PCR, 41 (91.1%) with virus isolation-IPX, 40 (88.8%) with IIPMA and 37 (82.2%) with IPMA. The results obtained indicated that RT-PCR is more suitable for the detection of BVD virus in frozen buffy coats stored for more than one year when compared to other techniques, and Ill can be used for the routine diagnosis of BVDV infection as an alternative technique to virus isolation-IPX.