Abstract A non-surgical blood exchange transfusion technique has been developed to obtain large amounts of antibody from individual rabbits immunized with groups A and C streptococci. Twenty-six of 30 rabbits survived one or more transfusions with blood from matched donors. Total yield of antibody to streptococcal polysaccharides from a single rabbit was between 2 and 21 g. Antibody levels were diminished as much as 90% by an exchange transfusion. Return of antibody levels to 50 to 100% of pre-transfusion levels was observed within 48 to 72 hr. Survival is not impaired by the use of non-matched blood in the transfusion procedure, although for immunologic reasons, matched blood is preferable. When it is not desirable to transfuse donor blood into the immunized rabbit, plasmaphoresis rather than exchange transfusion was employed. Plasmaphoresis, for example, was used for rabbits that produced high concentrations of 7S and 19S anti-IgG. In this way, possible cross-reactions between the recipient's anti-IgG and the serum IgG of the donor were avoided.