While a great deal of information can be gained from experiments conducted with laboratory rodents in vivo studies and with tissues and cells in vitro studies, there is a growing concern that mechanism of toxic action can be cell-, organ-, species- and even gender-specific. This concept has been appreciated for many decades in terms of reproductive toxicology, but is recently being openly accepted as a tenet in other toxicology sub-disciplines. Immune cell response to toxicants and response of immediate genes when compared between mice and human pathways are caveats regarding the extrapolation of results obtained from the rodent model to the human disease condition. When environmental hazards and their adverse effects are identified by epidemiologists in population-based studies, our current understanding of toxicology cautions that conventional animal models may not be appropriate for experiments to investigate mechanisms of toxic action of these substances or to establish safety, standards for them. Taken together, the new information at the cell and molecular level dictates that primate models, whenever possible, should be included in the complete design of modern toxicologic investigations. The goals of the Primate/Animal Models Facility Core are not only to provide materials but to identify opportunities and develop collaborations that will expand current Center activities to include studies with primates and primate materials. On request of Center faculty the Primate/Animal Models Facility Core personnel will identify the most appropriate California Regional Primate Research Center (CRPRC) staff member for consultation regarding current or proposed research activities. The specific aims are to optimize the use of the primate model in future Center research activities.