The objective of this monograph is to review the costeffectiveness of both external and internal migration control instruments in selected countries. In 2002, five industrial countries - the US, Canada, Germany, the Netherlands and the UK - spent about USD 17 billion to enforce immigration laws and to care for asylum-seekers, about two-thirds as much as they provided in Official Development Assistance. It may be argued that if countries targeted by irregular migration flows were to foster trade, investment and aid in the countries of origin, migration pressures could be expected to gradually decline, though programmes to promote local socioeconomic development able to encourage potential migrants to remain in their home countries can yield neither predictable nor quick results. There are no easy ways to narrow the gap between migration management objectives and the actual results achieved. The key to success posits the setting of realistic goals, coordinated migration management within and across countries and the continuing monitoring and revision of appropriate policy instruments since migrants, smugglers and others involved in the migration system tend to adjust their tactics and strategies very rapidly to such changes.