DNA extracted from ancient organic remains has much to offer anthropology and archaeology, but post-mortem damage can inhibit molecular biolosical techniques or produce incorrect sequence determinations. There have been few studies on the diagenesis of DNA and, as yet, little is known about how and why the molecule might survive over thousands or millions of years. Qualitative analysis of nucleic acids extracted from powdered bovine bone which had been heated to various temperatures in the presence and absence of water, revealed that the DNA had become fragmented. In the wet samples this decay was so extensive that mitochondrial DNA could not be amplified by the Polymerase Chain Reaction (PCR). Immunochemical detection of the DNA showed that substantial quantities of DNA remained in some samples for which a PCR product could not be obtained. The results of the DNA analyses are compared with theoretical estimates of DNA decay and protein survival in the same samples. Reasons for the disparity between the immunochemical and PCR data, such as interference of the PCR, are considered. It is concluded that hydrolytic chain scission events have much more impact on the loss of the long sequences of DNA required for PCR than on the numbers of shorter antibody binding sites detected by immunochemistry.