In particular, DNA typing of human leukocyte antigen (HLA)-DQA1 from single hairs is described, based on an analysis of freshly plucked hair samples obtained from 12 healthy Japanese. Hairs were separated into root and shaft portions, and DNA was extracted according to the protocol described by Higuchi et al. The specific region of the HLA-DQA1 gene was amplified by polymerase chain reaction (PCR). It was not easy, however, to type HLA-DQA1 with hair shaft portions. An increase in the specimens of hair shaft portions over 10 centimeters in length to obtain sufficient DNA inhibited the PCR. Synthetic melanin, as well as the one extracted from hairs, inhibited the PCR of the genomic DNA template when added to the PCR reaction at a concentration over 15 ng/100 micro L. The typability of hair shaft portions seemed to depend on the delicate balance of DNA concentrations and contaminated melanin in final DNA extracts. 22 references, 2 tables, and 3 figures (Author abstract modified)