A simple method, in which IgG but not IgM or IgA antibodies were absorbed, was used for removal of long-standing antibodies to rubella virus; when specific immunoglobulins were left, a recent rubella infection was indicated. Staphylococcus aureus (heated and treated with formalin) was added to sera; the sera were then separated from staphylococci by centrifugation. Sera from women with a recent rubella infection or from women to whom live rubella vaccine had been given recently showed unchanged or somewhat decreased hemagglutination-inhibiting antibodies to rubella virus, but still significantly more than were present in negative control sera. In contrast, S. aureus completely removed hemagglutinationinhibiting activity from all specimens of serum from women with anamnestically remote rubella infection. Similarly, the hemagglutination-inhibiting activity in the IgG fraction of chromatographically separated serum that contained long-standing antibodies could be completely abolished by absorption with staphylococci.