Animal models have played an important role in elucidating the nature of aging processes in general, and of behavioral aging specifically. Both aging and the behavioral processes of interest in this context are manifestly complex. Recent scholarship focusing on the nature of systems has provided new and varied conceptual schemata for addressing such intricacy. In this report, animal model systems are viewed in relation to some elementary systems notions. Limitations of the prototypical animal model are discussed, with particular emphasis on the implications of gene-gene and gene-environment interactions. These same interactions also provide opportunities. The traditional methods of genetic manipulation and control, combined with the powerful new tools of molecular genetics, and informed by systems considerations, offer broadened research horizons.