This chapter provides an overview of internal migration in China and reviews the institutions controlling migration. It examines the migratory patterns and characteristics and discusses relevant policy issues. In the pre-reform era, China practiced a policy of rural-urban segregation and rigorously controlled rural-to-urban migration. The rapid structural change of the Chinese economy and its transition from a planned to a market economy have eroded many of the previous migration barriers, resulting in a dramatic rise in population mobility. In essence, the hukou system in the pre-reform era functioned as a de facto internal passport mechanism. Any meaningful analysis of Chinese migration must start by looking at the hukou, or household registration system, which affects migration in many important ways. The socio-demographic and economic characteristics of migrants are significantly shaped by their motivations and opportunities for migration. It appears that economic factors have prevailed in most migration in China.