In the present investigation, we found that the catechol-O-methyltransferase activity (COMT) in erythrocytes of persons with severe thermal injury was strikingly increased when compared with that in erythrocytes of noninjured individuals. The specific activity of COMT in erythrocytes of burned patients was not correlated with extent of burn. Thus the echinocytes of burned persons are another example of abnormal red cells in which COMT activity is increased. This appears to be the first example of increased COMT activity in abnormal erythrocytes that is not associated with large numbers of reticulocytes.