We developed fluorescence-linked antigen quantification (FLAQ) assays for HIV-1 and SIV antigen quantitation. The assays utilize polystyrene microspheres coated with monoclonal antibodies against HIV-1 Gag p24 or SIV Gag p27, which are incubated with unknown samples, flourochrome-conjugated detector antibody, and lysing agent. The fluorescence of individual microspheres is measured using flow cytometry. The speed, simplicity, and wide dynamic range of FIAQ assays makes them superior to enzyme-linked immunosorbent assays for many applications performed in research laboratories.