Identification of cell-derived molecules on infectious human immunodeficiency virus type 1 (HIV-1) particles may be helpful in investigating mechanisms of HIV infection and in vaccine studies. Some of these molecules were detected on HIV-1 virions in previous studies, but rather elaborate methods were used. The method presented here allows an extensive characterization of the cell surface molecules associated with HIV-1 by capturing virus particles on monoclonal antibodies to cell membrane antigens bound to plastic wells. Binding of infectious virus was assessed by adding permissive target cells (C8I66) and determining viral replication. With this procedure, β₂-microglobulin, HLA-DR, intercellular adhesion molecule-1, and leukocyte function antigen-I were found on HIV-1 particles from laboratory strains and primary clinical isolates. In contrast, CDI9, CD4, and CD8 molecules were not detected.