"International labour migration involves 20 million workers from 'middle income' and 'Third World' countries. The article reviews both theoretical propositions and empirical evidence on its effects on regional disparities in labour exporting countries. It shows the variety of ways in which the departure of emigrants affects the uneven development of rural and urban areas there by changing the volume and nature of production as well as welfare conditions. Regional patterns of production and welfare are further modified by the impact of emigrants' remittances and their eventual return."