We used variance components analysis and offspring-parent regression to estimate the heritability of age at death in zoo populations of several species of mammals and birds. A meta-analysis over 14 species of mammals indicated a variance-component heritability of 0.53. More conservative regression estimates of heritability for the same species averaged 0.17. Offspring-parent regressions were not significant for any of eight species of birds. Heritabilities for data simulated with frailty and age-at-death models showed that sources of variation in age at death cannot be distinguished from observed heritabilities. The CV(A) in age at death in six mammal species, based on parent-offspring regression, ranged from 0.20 to 0.54. The absence of substantial genetic variation for age at death in birds might be related to the stringency of flight, allowing for little variation in the optimization of life-history trade-offs.