We have developed a sensitive, novel and efficient radioimmunopercipitation assay procedure, which provides conformation to ELISA and alternative to Western Blot assays for characterizing antibodies against human immunodeficiency virus-2 (HIV-2). We have used solubilized preparations of 1000X purified HIH-Z strain of HIV-2 virus spiked with purified recombinant HIV-2 gp-105 envelope protein, produced in the baculovirus expression system. Reaction of this spiked lysate with 1-125 including gp140, gp110, gp82 (dimer of gp41), p66, p34, p28 and p24. Sera from the CDC sensitivity panel and samples obtained from other sources were analyzed using this assay. This system provides a simple assay for characterizing and tittering antibodies against HIV-2, which is more specific than current ELISA methods. In addition, Bolton Hunter reagent treated proteins are well suited for biochemical studies. Future studies will use this assay to characterize the oligosaccharide side chains for gp110 and gp41 proteins to determine their role in the immune reaction.