Hematological profiles of the Formosan black bear (Ursus thibetanus formosanus). Zoological Studies 45(1): 93-97. Seasonal changes and sex differences in hematological values of 5 adult Formosan black bears, kept at the Low Altitude Experimental Station, Taichung County were evaluated from Apr. 2000 to Aug. 2003. Total erythrocyte counts, hemoglobin, hematocrit, and mean corpuscular volume were statistically higher in autumn-winter than in spring-summer but did not differ between sexes. Mean corpuscular hemoglobin was significantly higher in males than females but did not differ between seasons. Female total leucocyte counts and lymphocyte were statistically higher in spring-summer than autumn-winter, while monocytes showed the opposite response. This indicates that the innate immunological defense decreased with decreasing temperature. The other leucocyte differential count parameters, mean corpuscular hemoglobin concentration and total platelet count, did not differ among seasons or between sexes. These results suggested that from autumn to winter, erythrocytes are replaced by larger, more-numerous cells that increase oxygen transport, required for producing more energy. Baseline parameters established in this study will help evaluate diagnostic medicines that can be applied as guidelines for future management and preservation of Formosan black bears in the field.