Heritability estimates of viability of turkeys from 0 to 4 weeks of age averaged .080 ± .014 with a confidence interval (P < .01) of .044 to .094. Estimates of viability during cold stress and collection of blood at four weeks of age averaged .002 ± .012 with a confidence interval (P < .01) of -.028 to .032. The heritability estimate for viability from 0 to 8 weeks of age in several lines of medium weight and large weight turkeys was .117 ± .008 with a confidence interval (P < .01) of .096 to .138. Heritability estimates of the medium weight strains (.130 ± .010) averaged slightly higher than that of large weight strains (.096 ± .012). The magnitude of the heritability estimates increased with increases in mortality.