The thesis of the chapter has been that spatial delayed alternation versus position discrimination learning can serve as a valuable rodent model of cognitive development in neurotoxicology. The model captures dual-process conceptualizations of memory in human neuropsychology and involves procedures that are operationally very similar to those that have been used to address these conceptualizations in human and nonhuman primates. The model also captures the developmental profile and, at least in a general way, common neural mechanisms of cognitive development in human and nonhuman primates. Finally, the model reveals effects of heavy metals on cognitive development that would have been predicted from knowledge of the neuroanatomical effects of developmental exposure to these compounds. In addition, some of the work reveals properties of developmental neurotoxicity that resemble those claimed for environmental lead (Davis, 1990). In sum, the model system fulfills in a general way the criteria for animal models proposed earlier (and by investigators of other neurobehavioral disorders, Bartus & Dean, 1987; Solomon & Pendlebury, 1988).