No / There is developing interest in the analytical use of human hair from archaeological contexts in key research areas such as DNA, trace elemental and isotopic analyses. Other human tissues, especially bone, that have been used for trace element, isotopic and DNA analyses have had extensive study concerning their diagenesis, but this has not been done for hair. Consideration must be given to the complex interaction of hair with its buried environment, thereby laying a firm basis for the use of hair in future research. Since human hair is known to survive under a diverse range of environmental conditions, a pilot study has investigated the basic processes of hair degradation, using samples from different climatic zones and burial types. Variation in the degree of preservation of archaeological hair was characterized by light microscopy, electron microscopy, and FT-Raman spectroscopy, relating morphological change of the surface and internal structure of hair to its biochemical integrity. The results demonstrate a breakdown of cortical cell boundaries and disruption of the cuticular layering, coupled with infiltration of material from the burial matrix that suggests a progressive loss of cohesion that is in part due to microbiological activity. Medullated hair is shown to be more susceptible to physical breakdown by providing two routes for microbial and environmental attack. At the molecular level the proteinaceous component undergoes alteration, and the S-S cystine linkages, responsible for the strength and resilience of hair in living individuals, are lost.