In this chapter we consider the construction and use of population models to support reintroduction decision making. We begin by reviewing the decision-analytic process, also known as structured decision making. The material on structured decision making builds on the chapter by Chauvenet et al. (This Volume) who focus their attention on the objective setting step of structured decision making. In a decision-analytic setting, modeling cannot commence before objective setting, because the purpose of models is to provide predictions about how different management alternatives will influence the attainment of management objectives. After the introductory section on structured decision making, we turn our attention to the construction and use of population models. We discuss the steps in modeling, including structuring and planning models, obtaining parameter estimates from data, filling information gaps using expert judgment, constructing models, and using models to evaluate action alternatives. We close the chapter with a discussion of research and development needs that we believe will advance the use of population models to support the effective management of reintroduced populations.