The sex ratio of mortality has important social implications but is only rarely considered. Women have lower mortality rates than men. The sex ratio of mortality is cause-specific and differs markedly between populations. Assuming that the genetic differences between the sexes are very similar between populations implies that the differences in the sex ratio cannot be explained by genetic factors. Gender differences in smoking levels exert a strong influence on the sex ratio of lung cancer, total cardiovascular and all-cause mortality. The sex ratio of mortality decreases with age. The mortality rates between the genders are highly significantly correlated (p < 0.0001) both at younger and older age classes, except for lung cancer in the 45-74 y age class. This demonstrates that identical factors influence the mortality rates of both genders, but at a lower level in women.