We provide a structural theory of time preference and derive a functional form of intertemporal preferences by postulating that individuals make their life-cycle choices as if to maximize expected lifetime. This approach yields a non-time-separable expected utility representation. The rate of time preference is found to depend on the inverse of expected remaining lifetime and on the effect of age on the productivity of consumption in affecting health. Preferences display nearby complementarity and are such that the inverse of the coefficient of intertemporal substitution exceeds the coefficient of relative risk aversion.