The identification of blood proteins in ancient bone is important for the following reasons: 1) detection of simple proteins can give information on species specificity and evolution; and 2) the methods used provide a sound technical basis for investigating the survival of more informative proteins, such as HLA and blood groups, which would shed light on genetic profiles and disease predispositions of ancient populations. Previous studies used a sensitive and specific enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies and showed that albumin can be identified in human skeletal remains at least 4,000 years old. However, the factors that affect survival and diagenesis of proteins within ancient bone remain largely unresolved. The present studies compare the results obtained after testing extracts of ancient bovine and human bone for albumin with the ELISA. Although albumin could be detected in both bovine and human bones that were several thousand years old, the survival pattern between the species was strikingly different (chi-square=11.7, Pless than0.001). Albumin was identified in 23 of the 31 human extracts, but in only two of the 14 bovine extracts. The authors conclude that bone integrity is of great importance for protein survival and that exposure of marrow and trabecular bone to the physical and chemical effects of water is the most significant single factor in the production of diagenetic changes. In this respect, water appears to have a far greater effect than age, soil content, pH, or heat.