Antibodies to HIV are potentially important reagents for basic and clinical studies. Historically, these reagents have been produced by random cloning of heavy and light chains in phage display libraries [Burton, D.R., Barbas, C.F. III, Persson, M.A.A., Koenig, S., Chanock, R.M., and Lerner, R.A., (1991), A large array of human monoclonal antibodies to type 1 immnodeficiency virus from combinatorial libraries of asymptomatic seropositive individuals. Proc. Natl. Acad. Sci. U. S. A. 88, 10134–10137.] and electrofusion techniques [Buchacher, A., Predl, R., Tauer, C., Purtscher, M., Gruber, G., Heider, R., Steindl, F., Trkola, A., Jungbauer, A., and Katinger, H., (1992), Human monoclonal antibodies against gp41 and gp120 as potential agent for passive immunization. Vaccines 92, 191–195]. Here we describe a method to identify and potentially enrich human memory B cells from HIV infected patients that show serum titers of neutralizing antibodies. When biotinylated gp140 is used to stain peripheral blood mononuclear cells it identifies a distinct population of gp140 binding B cells by flow cytometry.