The total carbohydrate content of purified hepatitis B antigen (HB Ag) ranged between 3.6 and 6.5% as determined by the phenol-sulfuric acid method. Disc-sodium dodecyl sulfate PAGE of purified HB Ag followed by periodate-Schiff staining revealed one major and two minor glycoproteins with molecular weights of 22,000,27,000 and 32,000 daltons, respectively. Both ad and ay subtypes of HB Ag contained these glycoproteins.