Antibody anti-Human F(ab')2 phycoerythrin conjugated is suitable for immunomicroscopy and flow cytometry or FACS analysis as well as other antibody based fluorescent assays requiring extremely low background levels, absence of F(c) mediated binding, lot-to-lot consistency, high titer and specificity. The maximum amount of reagent required to stain 1 x 10E6 cells in flow cytometry is approximately 1.0 ug of antibody conjugate.