Residues of blood, tissue, hair, feathers, and other animal and plant materials have been found on the surfaces of prehistoric tools which range widely in age and location. Research using microscopic and biochemical methods to detect such residues and to identify the species of origin has been completed. To develop routine methods for separating and identifying residues, studies are continuing that use more sophisticated techniques such as iso-electric focussing and radio-immuno assay. The presence of still-active biomolecules and proteins on large numbers of tools from differt ages and locations, coupled with increasingly sensitive techniques for the study of very small amounts of material suggests potentially useful lines of archaeometric research. Possibilities include immunological studies of ancient human populations, stable isotope studies to determine diet and environmental parameters of humans and animals, and site location and size measurement by biochemical determination of tissue byproduct molecules like cholesterol. In some cases it may be possible to obtain enough organic residue from tools so that a radiocarbon date may be made using the new accelerator technique. Thus time-of-use of stone tools could be determined. Many of the techniques are speculative but are founded on currently available methods. A clear demarcation between possible, probable, and speculative applications is made in this paper.