The characteristics of various animal models and their relevance for aging studies have been briefly discussed above. These are summarized in tabular form in Tables 1A-1F. The appropriate choice of a model for studying aging depends on a multitude of factors, but the most important characteristics appear to be relevance to human aging, manipulability of the genetic system, availability of physiological characterization data, and ease and cost of husbandry. Whereas most of the organisms discussed here do not satisfy all these criteria, they do offer some special opportunities, for example the ability to study calcium metabolism in female birds; to manipulate the rate of aging in lizards; and to study the genetics of life span in insects (e.g., Drosophila) and/or nematodes. We hope that the information collected here will prove useful to gerontologists with special interests related to human aging, and readers are encouraged to contact the various participants of this workshop for additional information.