Diagnostic significance of electrophoretic findings of serum protein in cows with traumatic pericarditis was evaluated. Affected cows were classified into 3 groups according to autoptical findings: fibrinous, sero-fibrinous, and purulent types. Slight hypoprotenemia, moderate hypo-albuminemia, slight hyper-α globulinemia and tendency of hyper-β globulinemia were commonly observed in the affected cows. The level of γ globulin tended to be lower in the cows with fibrinous or sero-fibrinous, and higher in purulent pericarditis than the level in healthy cows. In the serum protein electropherograms of the cows with fibrinous or sero-fibrinous pericarditis, there was pathognostic pattern composed of slender albumin, acute shape of α globulin with a broad rising accompanied by double peaks and with main peak migrating toward the albumin side, tendency of rising β globulin fraction, and large indentation between β and γ fractions. These findings except for the slender albumin fraction, however, was not or poorly observed in purulent pericarditis. Electrophoretic findings were subacute inflammatory pattern with non-selective serum protein losing in fibrinous or sero-fibrinous, and chronic inflammatory pattern in purulent pericarditis. © 1991, JAPANESE SOCIETY OF VETERINARY SCIENCE. All rights reserved.