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BY means of chromatography and electrophoresis on starch gel, Morell and Scheinberg1 showed at least four different molecular components of ceruloplasmin in preparations from the plasma of 9,109 human donors. Then McAlister et al.2 presented evidence for multiple ceruloplasmin components in human sera. Using vertical starch-gel electrophoresis to resolve the ceruloplasmins combined with direct chemical and enzymatic analysis on the gel, they defined five distinct proteins having one or more characteristic properties of ceruloplasmin. The enzymatic analysis used by these workers was based on the work by Holmberg and Laurell3, who showed that ceruloplasmin could oxidize a number of substances, the best substrate being p-phenylenediamine (PPD). Using the PPD oxidase activity as a measure of the ceruloplasmin in sera of different species, it was shown by McCosker4 that pig sera has more than twice the activity of human sera and four times that of other domestic species.