There are a number of reasons to use Drosophila as a model system to study cell migration. First and foremost is the availability of an arsenal of powerful genetic techniques that can be deployed, permitting the study of cell migration in vivo, in the context of the entire organism. This is especially important for the study of a complex behavior that can be dramatically affected by small changes in environmental conditions. Several different types of cell migrations occur during Drosophila development. In this chapter, we focus on cell migrations that have been subjected to the most intense scrutiny. We describe each of the cell types and their trajectories and provide information regarding markers that are useful for the study of each cell type and mutations that affect their migrations. In addition, we provide protocols for staining embryos and manipulating gene function in each of the migratory populations. Finally, we offer some advice concerning the analysis and interpretation of mutant phenotypes.