Identifying the mechanisms determining species-specific life spans is a central challenge in understanding the biology of aging. Cellular stresses produce damage, that may accumulate and cause aging. Evolution theory predicts that long-lived species secure their longevity through investment in a more durable soma, including enhanced cellular resistance to stress. To investigate whether cells from long-lived species have better mechanisms to cope with oxidative and non-oxidative stress, we compared cellular resistance of primary skin fibroblasts from eight mammalian species with a range of life spans. Cell survival was measured by the thymidine incorporation assay following stresses induced by paraquat, hydrogen peroxide, tert-butyl hydroperoxide, sodium arsenite and alkaline pH (sodium hydroxide). Significant positive correlations between cell LD₉₀ and maximum life span were found for all these stresses. Similar results were obtained when cell survival was measured by the MTT assay, and when lymphocytes from different species were compared. Cellular resistance to a variety of oxidative and non-oxidative stresses was positively correlated with mammalian longevity. Our results support the concept that the gene network regulating the cellular response to stress is functionally important in aging and longevity.