Sera from normal bighorn sheep (Ovis canadensis) and bighorns with chronic pneumonia attributed to Mycoplasma and bacteria were analyzed by cellulose acetate electrophoresis. Diseased sheep had significantly (p = <0.001) lower albumins, higher α1 and γ globulins, and A/G ratio below 1.0. The electrophoretic patterns, while not disease specific, provide means for detecting sub-clinical chronic disease and monitoring responses to therapy in bighorn sheep.