Skin surface biopsies taken from normal and parakeratotic skin and stained with a 4-4-diamidinodiphenylamine dihydrochloride (M & B 938) were examined microscopically using bright field and ultraviolet light illumination. No fluorescence was seen in squames from normal skin when microscopically examined using ultraviolet light illumination. In marked contrast, brilliantly fluorescent nuclei were observed in squames from parakeratotic skin. Control preparations treated with DNAse and stained with M & B 938 did not exhibit nuclear fluorescence. The fluorochrome is not specific for DNA since it stains cartilage and goblet cells and appears to behave as a basic dye.