A method of electrophoresis utilizing cellulose acetate is described wherein quantitation of serum protein fractions by densitometry is accomplished within 2 hr. of initiation of the procedure. The densitometer was found to have a linear response to amido black dye. Albumin and y-globulin demonstrated equal dye-binding characteristics. Combined with the absence of albumin trailing, this has afforded excellent quantitations of serum protein fractions.