My thesis dissertation focuses on the temporariness of migration, its diverse effects as well as on migration selection. The first paper, A Dynamic Model of Return Migration analyzes the decision process underlying return migration using a dynamic model. We explain how migrants decide whether to stay or to go back to their home country together with their savings and consumption decisions. We simulate our model with return intentions and perform policy simulations. The second paper, Remittances and Temporary Migration, studies the remittance behaviour of immigrants and how it relates to temporary versus permanent migration plans. We use a unique data source that provides unusual detail on the purpose of remittances, savings, and return plans, and follows the same household over time. Our results suggest that changes in return plans lead to large changes in remittance flows. The third paper, Savings, Asset Holdings, and Temporary, analyzes how return plans affect not only remittances but also savings and the accumulation of assets. We show that immigrants with temporary return plans place a higher proportion of savings in the home country and have accumulated a higher amount and share of assets and housing value in the home country (compared to the host country). Finally, the fourth paper, Migrant Selection to the U.S.: Evidence from the Mexican Family Life Survey (MxFLS), studies the selection in terms of skills of recent migrants to the United States using the MxFLS. We highlight the important age gradient of migration, the different education attainment between age cohorts in Mexico and show the implications when analyzing migrant selection. Our claim is that in order to properly study the self-selection of migrants, it is necessary to compare migrants to non-migrants of the same age cohort.