Abstract
A normal human serum examined by Laurell's crossed electrophoresis using anti whole human serum gave 42 precipitation arcs. Examples are given of identification of the individual precipitate based on the electrophoretic posi tion, the use of known antigens and antibodies, specific staining methods, and fractions of serum from Sephadex G-200 chromatography and salting out with ammonium sulfate. By these methods it has been possible to name 26 precipitates.