Electrophysiological study of transiently transfected cells requires the identification of individual cells that express the protein of interest. We describe a simple, quick and inexpensive method for visually identifying cells that have been co-transfected with an expression plasmid for a lymphocyte surface antigen (CD8-alpha). Transfected cells are incubated briefly with polystyrene microspheres (4.5 microns diameter) that have been precoated with antibody to CD8. Cells expressing CD8 on their surface are decorated with many beads and are thus readily distinguishable from untransfected cells. Beads already coated with antibody are available commercially. The method takes less than five minutes and requires no reagent preparation or special equipment for visualization of the beads.