Abstract: A method of isolating alpha.sub.1 -fetoprotein sufficiently pure to be useful in radioimmunoassay procedures is described. The method comprises the procedures and techniques of affinity chromatography, immobilized reactive dye adsorption chromatography and polyacrylamide gel electrophoresis. Wherein a certain degree of reduction in kind and/or quantity of contaminants is not achieved by the first two procedures, gel filtration and mixed ion exchange cellulose chromatography are carried out in preparation for polyacrylamide gel electrophoresis. Monkey alpha.sub.1 -fetoprotein very similar to human cord blood alpha.sub.1 -fetoprotein by amino acid composition and physical properties and of sufficient purity to be useful in human radioimmunoassay procedures is obtained by the disclosed method.

Abstract: A method of isolating alpha.sub.1 -fetoprotein sufficiently pure to be useful in radioimmunoassay procedures is described. The method comprises the procedures and techniques of affinity chromatography, blue dextran adsorption chromatography and polyacrylamide gel electrophoresis. Wherein a certain degree of reduction in kind and/or quantity of contaminants is not achieved by the first two procedures, gel filtration and mixed ion exchange cellulose chromatography are carried out in preparation for polyacrylamide gel electrophoresis. Monkey alpha.sub.1 -fetoprotein very similar to human cord blood alpha.sub.1 -fetoprotein by amino acid composition and physical properties and of sufficient purity to be useful in human radioimmunoassay procedures is obtained by the disclosed method.