Characterize of B. bigemina antigen (Egyptian strain) using SDS-PAGE and immunoblotting technique was performed in order to study the protein components of B. bigemina (Egyptian strain, which help in accurate diagnosis of the parasitic. Running of B. bigemina isolate on 10-15% polyacrylamide gradient gel (phastsystem. Pharmacia, Sweden) was carried out. Staining of the gel with silver nitrate showed 3 maior polypeptide components of molecular weight 85.6 and 53 KDa. Other descrinable band with molecular weighis of 47,3, 33 and 26 KDa The western transfer analysis using “BIO-RAD, USA) showed that antiserum From animals experimentally infected with B. bigemina contained detectable antibodies directed against only  proteins at the molecular weights of 61, 53 KDa.