A technique is described for prescreening the oral cavity for cancer by analyzing the fluorescence of dilute solutions of acriflavine hydrochloride after staining cells obtained by self-irrigation or swabbing. The dye is practically specific for cellular nucleic acids. The method allows extremely sensitive determinations with relatively simple apparatus. Homogeneous cell samples are obtained by filtering out nonspecific smaller cells using membrane filters with 10μ pores. Early clinical results obtained to date indicate sharp quantitative differences, ascribed to variations in cellular nucleic acid content, between normal cells, cells of heavy smokers, leukoplakia and malignancies. These quantitative automated data can be correlated with conventional cytological preparations made simultaneously from the same cells. The significance of these measurements is discussed.