By the method of affinity chromatography a partially purified antigen was obtained after passing the plasma of an asymptomatic carrier of HBs Ag through a column of Sepharose 4 B linked to angi-HBs. This antigen was inoculated in rabbits using a schedule of 1.0 mg in the first dose and 4 other doses of 0,5 mg with intervals of approximately 15 days. Observing that blood samples colletcted after the 5th inoculation showed no change in antibody levels, the animals were bled on the 62 th day and these immune ser were standardized with the following tests for the detection of HBsAg: a) reverse passive hemagglutination (R-PHA) – using specific gamma globulin that was obtained from rabbit sera by affinity chromatography and reaching an optimal concentration of 10µg/ml to sensitise SRBC at 5% fixed in glutaraldehyde. b) Counter immuno electrophoresis (CIEP) – using the rabbit immune sera diluted to 1/20 as a reagent for the detection of HBsAg. The immune sera was also used to conjugate new Sepharose 4B for affinity chromatography and was found having a linking capacity of approximately 0,5 to 1,0mg of HbsAg per ml of Sepharose after complete saturation.