The concentrations of the acute‐phase proteins, serum amyloid‐A (SAA) and haptoglobin (Hp), were determined in the plasma of healthy cows (n=25) and cows with spontaneous acute (n=6), subacute (n=37), or chronic (n=7) inflammatory diseases. The plasma concentration of SAA alone, Hp alone, and the Hp/SAA ratio, differed significantly (p<0.001) between healthy animals and animals with inflammatory diseases. Plasma Hp concentrations in the group of cows with acute inflammatory diseases were significantly (p<0.01) different from those in the group with chronic inflammatory diseases. Moreover, the Hp/SAA ratio in chronic inflammatory diseases was significantly different from this ratio in acute (p<0.01) and subacute (p<0.05) inflammatory diseases. It is therefore concluded that the plasma concentrations of SAA and Hp and the Hp/SAA ratio are useful parameters to distinguish healthy animals from animals with inflammation and can be helpful in distinguishing between acute and chronic of inflammatory diseases.