This document discusses the difficulties of measuring internal migration and examines the use of the migration module of population censuses to build migration matrices. Different ways of interpreting the intensity of internal migration are outlined and the corresponding existing indicators are explained. Four direct sociodemographic effects of internal migration —growth, redistribution, composition and inequality— are then described, along with the measurement procedures and indicators for all four. Selectivity of migration and indirect measurement of migration are also discussed. The last point analysed is another form of population movement —commuting for work or study— and how it can be measured using census data. The document concludes with a summary of the available instruments and the challenges that must still be overcome to measure spatial mobility of the population in Latin America in a specialized and rigorous manner.