The impact of human handling on studies of blood residues is demonstrated by experimental work undertaken on modern stone tools. The results are examined within the context of excavation techniques and conservation treatments that may influence laboratory analyses, with special emphasis on the consequences of washing and handling stone artifacts. The results of experimental work are compared with those obtained from a large assemblage of stone tools that was excavated along the shore of the Anacostia River in Washington DC. Because the amount of biomolecules found on excavated materials are small, more sensitive biochemical techniques are being applied to archaeological artifacts. The implications of organic residue analysis for archaeologists, conservators and collections managers are considered, with emphasis on appropriate methods of excavation, treatment procedures and materials for storage. This paper focuses on the issues of immediate concern to conservators, and the impact that washing and handling may have on residue analysis. -- ICCROM