The extraction and identification of deoxyribonucleic acid (DNA) from human hair shafts is described, along with the effects of hair treatments on levels of DNA and suggestions of DNA location within the shaft. DNA was present at low levels in the hair shaft, and was identified using polymerase chain reaction amplification of the human leukocyte antigen (HLA)-DQA1 locus. The use of cleanup columns aided the success of PCR amplification. DNA appears to reside in the cuticle portion of the hair shaft. Levels of DNA were found to be higher at the root-end compared to the tip-end of hair and were also found to be lower after permanent colorant treatment. DNA was found to be lost with surfactant washing, with increased loss occurring with prolonged or an increasing number of washes. These results suggest that small amounts of residual DNA remain after differentiation and add to our knowledge of the constituents of hair.