PIP: The persistence and widespread nature of undocumented migration in Africa is due to 1) the absence of barriers or the arbitrariness of national frontiers, 2) the large stretch of unpoliced borders, 3) ignorance about the existence of borders, and 4) the absence or inadequacy of migration laws and regulations in both the countries of origin and destination. The free movement of persons in Africa has a long tradition. Over a large part of Africa, international migration is regarded as an extension of internal migration. The free movement of persons across frontiers in Africa historically has been facilitated by the cultural affinity of communities divided by international boundaries and the colonial policies of both the French and British. The "migration" of nomads pays little regard to international borders and is largely undocumented, even in national censuses. The frontier workers along the borders of Uganda and Kenya where members of the same extended family live on both sides of the borders and commute daily are statistically regarded as international migrants, without regard for the sociocultural realities of the African situation. Political independence substantially altered the erstwhile free movement of persons across African countries as national governments enacted immigration laws and regulations. The newly independent countries wanted to reserve employment for nationals. The Sahelian drought, internal strife in Chad, the deteriorating economic situation in Ghana, the oil-lead economic boom in Nigeria, and the treaty on the free movement of people in the community accelerate the tempo of undocumented migration in West Africa. Also, migration laws and regulations are not always rigorously enforced. Expulsion and deportation are common policy measures directed at illegal migrants resident in African countries. In Nigeria, the events leading to the expulsion of aliens were gradual, but in all cases, the actual expulsion--or decisions to expel--are usually sudden and dramatic.