The characterization of genetic variation at the level of DNA has generated significant advances in gene mapping and disease diagnosis, and forensic identification of individuals. It is now possible to identify individual DNA from various tissue specimens, like hair, using the PCR and oligonucleotide probes. To date, however, the number of hairs needed, the preservation conditions, and the kinds of hair suitable for DNA extraction have not been well known. We performed DNA extraction using hairs from different body sites, using different numbers of hairs, under various different preservation conditions to investigate the acquisition conditions of DNA data from hair using PCR and specific HLA-DQA probe. HLA-DQA genotyping of DNA extracted from peripheral blood was performed to compare the results of hair and blood HLA-DQA genotyping from individuals. The results are as follows: 1) The concentration of DNA extracted from a single strand of hair is 5.23+/-0.54 g/ml. It is possible to extract sufficient DNA for HLA-DQA genotyping from a single strand of hair. 2) DNA concentration is different according to body site. Concentrations are 7.01+/-0.33 g/ml in scalp hair, 6.28+/-0.29 g/ml in axillary hair, and 6.10+0.24 microgram/ml in pubic hair. 3) There is no difference between the electrophortic bands resulting from DNA extracted from the hair of an individual preserved under different conditions, such as room temperature, exposure to sunlight, exposure to low temperature (+4degrees C), or exposure to moisture. 4) There is no difference between the electrophoretic bands resulting from DNA extracted from hair of a single individual preserved for different lengths of time. 5) In an individual, the HLA-DQA genotype obtained from peripheral blood is identical to that obtained from hair. Even though the amout of DNA obtained from hair is limited, it is possible to identify the HLA-DQA genotype of an individual using a single strand of hair. This requires adequate extraction of DNA for PCR analysis using an allele specific probe. We believe that HLA-DQA genotyping using the PCR method on DNA extracted from hair is useful for disease diagnosis and forensic science.