Hemoglobin concentration, hematocrit, erythrocyte diameter, and total and differential leukocyte counts were obtained from five male and seven female gray squirrels. Plasma glucose, corticosterone, and cholesterol concentrations were determined for the five males and for six of the females.The males showed significantly greater values for the hemoglobin and hematocrit. The average leukocyte count was lower than reported values for several other rodent species. Lymphocytes formed a greater percentage of the leukocytes than usually reported for rodent species.No sex-related differences were apparent with respect to the plasma concentration of glucose, corticosterone, and cholesterol. The gray squirrel appears to have a relatively high normal level of corticosterone and cholesterol.