Analysis of the hypothesis that the mortality level is an important determinant in parents' decisions about family size and the quality of their children. For family decisions, the important property of a broad reduction in mortality is that it leads to proportionately greater increases in probability of survival from any given age to successively older ages. Assuming that rewards rise with age relative to costs, so that parents feel better off, all things considered, the longer a child survives, a mortality decline increases the expected return from a decision to have a child relatively more than it increases expected costs. The analysis suggests that a decline in mortality level may influence household decisions concerning children by (1) increasing family resources devoted to children; (2) causing more family resources to be spent on quality attributes; and (3) altering family response to changes in other environmental constraints and opportunities important for fertility decisions. 41 pp. Ref.