Why are there differences in life expectancies among various demographic groups? Why have these changes in life expectancies occurred? Many reasons are given in the popular and more scholarly literatures. Considering an integrated approach to investigating determinants and correlates of mortality in the United States, this text integrates modelling, micro data, and modern econometric techniques. A number of examples of applications are included, with some explorations of the robustness of the results under alternative assumptions. The basic purpose of this text is to increase our knowledge of mortality and to illustrate how such an integrated approach can further our knowledge of mortality and related phenomena.