The amount of hemoglobin per unit volume of the blood, hemoglobin content of individual red blood cells, and the concentration of hemoglobin in each red blood cell increased in beef calves (Hereford and Angus) with increases in body weight from 500 to 800 lb. The number of red blood cells decreased with increased body weight. The number of white blood cells, lymphocytes and monocytes decreased with increases in body weight while the number of neutrophils, eosinophils and basophils were variable from weight to weight.