This paper develops a simple two-country model of international migration. By distinguishing individuals in terms of their ability and age, the model enables us to examine not only the equilibrium flow of migrants and the pattern of factor rewards in the two economies, but also the factors which determine the skill and age profile of those who migrate. In addition, the effects of both qualitative and quantitative restrictions on immigration are analysed within a general-equilibrium framework. The role of an emigration tax and how it interacts with the immigration policy of the labor-importing country is also considered.