The modern literature on the economics of immigration focuses on 3 related issues: 1) what determines the size and skill composition of immigrants flows to any particular host country; 2) how do the immigrants adapt to the host country's economy; and 3) what is the impact of immigrants on the host country's economy? This article reviews the theoretical framework and empirical evidence provided by the economics literature on these questions. It demonstrates that the economic approach, using the assumption that migration behavior is guided by the search for better economic opportunities and that the exchanges among the various players are regulated by an immigration market, leads to substantial insights in to these issues.