Cellulose—acetate electrophoretic densitometry patterns for α2-globulin have been analyzed, with sera from 150 patients. The mobility of serum α2-macroglobulin exceeds that of haptoglobin to the extent that certain patterns correlate with abnormal concentrations of one or both of these proteins in serum. The most readily recognizable patterns occur when there is a major increase in one protein and the other remains normal. A very low value for one protein, particularly haptoglobin, can also be recognized. Concentration of these two proteins can be roughly predicted under definable circumstances.