It is the main purpose of the book to give a logically consistent foundation of migration decision making under incomplete information in a unified framework. Decision rules for migration are derived from a general model of Stochastic Dynamic Programming and the properties of temporary migration equilibria are discussed as well. Finally, some hints are given for esti- mating the theoretical models which are elaborated in the book. Many results concerning the properties of optimal migration policies and of temporary migration equilibria are new. For example, it is demonstrated that less information about a country might it make more attractive for immigration, and conditions are analyzed that imply the existence of a significant stream of migrants even between identical countries in a temporary equilibrium state. The book is written for the mathematically oriented reader in economics, operations research or econometrics who is interested in application of Stochastic Dynamic Programming to an important field of research in population economics.