Recent economic and aesthetic interest in North American bison (Bison bison) has lead to increased interstate transport of these animals. Serologic and hematologic standards for bison are needed to detect disease in transported animals as well as within herds. This paper describes variation in blood physiological parameters in bison caused by variations in diet and season. Blood was taken from six bison and analyzed for serologic and hematologic parameters. Significant variation was found in blood urea nitrogen, chloride, cholesterol, creatinine, eosinophil, glucose, hemoglobin, lactic dehydrogenase, leukocyte, packed cell volume, potassium, serum globulin, serum glutamic oxalacetic transaminase, SGPT, and sodium levels between animals receiving a high energy-high nitrogen diet and animals receiving a low energy-low nitrogen diet.