Alpha-1 acid glycoprotein, also named orosomucoid (ORM), is a serum protein with genetic polymorphism. This paper describes a two-step procedure for purifying ORM from human sera. The procedure consists of both anion exchange chromatography on a DEAE-Sephadex-A50 column and affinity chromatography on a Reactive Blue 2-Sepharose CL-6B column. The purified ORM identified by polyacrylamide gel electrophoresis, SDS-polyacrylamide gradient gel electrophoresis, immunoelectrophoresis and immunodiffusion was homogeneous and reacted specifically with a commercial anti-ORM serum (Sigma). The molecular weight of the purified ORM was about 41 kd.