Knowledge about B-cell dysfunction and HIV-specific antibody production is necessary for the understanding of both HIV-1-related immunopathology and the (vaccine-induced) humoral immunity involved in protection against AIDS. This paper describes the application of recently developed methods to detect epitope specificity of B cells in lymph-node biopsies with antigen–enzyme conjugates. Cryosections of five lymph-node biopsies from HIV-1-infected individuals and four control tissues were stained with a panel of HIV-1 antigen–enzyme conjugates: recombinant HIV-1 proteins (gp160, gp120 and p24), labelled with peroxidase, and synthetic peptides representing neutralizing epitopes from gp120 and gp41, labelled with alkaline phosphatase. Antibody-forming cells (AFCs) were detected in all the HIV-1-infected biopsies with gp160, gp120 and/or p24, in numbers up to 350 per section. AFCs producing specific antibodies against peptide 101 (SP 101), representing the neutralizing epitope 586–608 of gp41, were detected in one patient. These techniques allow correlation ofin vivofunction of–B cells with lymph-node pathology, clinical stage of the disease and serological data. Their potential for the elucidation of HIV-related immunopathogenesis and the development of vaccines is discussed.