Paraformaldehyde-induced fluorescence in frozen-dried tissues survives embedding in glycol methacrylate. After freeze-drying and treatment with paraformaldehyde vapor, tissues to be examined by this technique are immersed in glycol methacrylate and placed in a dessicator which is then evacuated. They are usually left overnight in the dark; next day, the polymerizer is added and the tissues are again left overnight in the dark in the evacuated dessicator; for smaller blocks or certain tissues, these times can be shortened. The blocks are cut on a JB-4 microtome. Sections of 1-10μ can be made readily with a dry glass knife according to standard procedures.