Aqueous glutaraldehyde has been polymerized under alkaline conditions in the presence of a surfactant to yield microspheres of varied diameters. Microbeads of a nominal 300 nm diameter, made fluorescent via fluoresceinisothiocyanate, were used as a carrier of rabbit anti-human red blood cell antibodies. Specific labeling of the human red blood cells as well as diagnostic use of these fluor...