Chromatographically purified rabbit albumin. Purified rabbit albumin may be used as a reference antigen, calibrator, coating protein and blocking agent in a variety of immunoassays including immunodiffusion, immunoelectrophoresis, ELISA, Western blotting, dot-immunobinding assays (DIBA), haemagglutination, and cellbinding assays. Not less than 98% as determined by agar-gel electrophoresis. Tested in a concentration of 40 mg/ml at the level of sensitivity of the applied immunoprecipitating techniques, this product contains only a trace of an alpha 1 protein.