Анотация: This study was designed to determine a reference range of haptoglobin (Hp) in Iranian Holstein cattle of different ages and of both sexes, and to evaluate Hp as marker in some inflammatory diseases in Shiraz, a tropical area in southern Iran. Blood samples were collected from the coccygeal vein of 50 clinically healthy cattle and 36 cows with various inflammatory diseases (acute diffuse traumatic reticuloperitonitis, digestive tract infection and abomasal displacement, anaplasmosis, theileriosis, acute respiratory infections and clinical mastitis). Hp was measured according to preservation of the peroxidase activity of haemoglobin which is directly proportional to the amount of haptoglobin. There was no significant difference in Hp concentrations between healthy Holstein cattle from the studied different age groups as well as between both sexes. Pregnancy and lactation had no significant effects on blood Hp concentrations. Statistically significant differences in Hp were observed between clinically healthy and diseased cows (P<0.05). The results of the present study revealed that serum Hp was a sensitive factor in various inflammatory conditions in cattle