This study was preformed between 2003 and 2006. One hundred and sixty five blood samples were collected from BTV infected sheep of each district of Coimbatore, Dindigul, Erode, Karur, Namakkal and Salem. Out of 165 samples 13 are positive both RT-PCR and nested PCR. In nested PCR minimum RNA was amplified. Hence, the diagnosistic sensitivity of nested PCR greater than the RT-PCR. The accuracy in diagnosis, more sensitive and specific assays, such as those based on antigens produced by recombinant DNA technologies and the polymerase chain reaction should prove useful.