X-chromatin in the nucleus of hair cortex cell was stained by Feulgen reaction after bleaching melanin granules, and the frequency of X-chromatin was calculated under an ordinary microscope. In another method, fluorescent Feulgen reaction with acriflavine using a fluorescence microscope was attempted. The results obtained from both methods indicated significantly higher values in the female samples than those in the male samples. The frequency of Y- chromatin was determined after quinacrine staining with the use of a fluorescence microscope; male and female samples were distinguishable with this method. Using a single specimen, sex determination from the frequency of X- or Y- chromatin was practicable through combined treatment of quinacrine staining and fluorescent Feulgen reaction. These methods worked during 16 to 64 weeks for samples that were kept dry. The study concluded that sex determination from frequency of sex chromatin as determined by the described methods is reliable. 9 figures and 16 references