Industrialisation in European countries caused an increase in both internal migration and emigration. Internal migrants were even more numerous than overseas emigrants. However, few empirical studies have sought to explain internal migrations. This article examines the causes and effects of internal migration in Spain with the aim of answering some of the questions debated in the literature. The results show that internal migrations in Spain were driven by economic forces. Moreover, the lag in rural population transfer can be explained by the scant pull of industrial and urban destinations. The article also shows that internal migrants differed in some respects from the people who emigrated overseas. Finally, the impact of internal migration on labour markets is measured.