The expulsion of Ghanaians and other illegal immigrants from Nigeria is the latest in a number of mass deportations ordered periodically by black African nations since gaining their independence in the last quarter century.

As Africa's most populous nation, Nigeria has ordered the biggest deportations.

More than a million Ghanaians were deported in 1983, when Nigeria first expelled illegal aliens, and officials in Lagos, the Nigerian capital, say Ghanaians account for 300,000 of the nation's 700,000 currently unwanted immigrants.

But Nigeria is not the only African country to order large-scale deportations.

The first recorded expulsions in postcolonial Africa were ordered by the government of Dahomey, a small former French possession located just to the west of Nigeria and now called Benin.

Because of long established Christian missionary schools, Dahomeyans were among Africa's best-educated people, and served throughout the once vast French African empire as civil servants in the colonial bureaucracy.

When France's black African colonies gained independence within months of each other in 1960, many Dahomeyan bureaucrats were discharged, and their jobs given to nationals who often had less education. Many African states have expelled entrenched foreign minorities in a similar fashion.

Deportations have become so common that few governments now issue more than pro forma protests. But the confusion and apparent mishandling of Nigeria's current operation have given rise to controversy.

Almost any pretext will justify such expulsions: in one case it was a fistfight at an international soccer match.

Africans pay little heed to visas and other formalities in a part of the world where international borders are porous and often artificially drawn as a result of European colonization in the 19th century.

Traditional migratory patterns, for example, have attracted labor from such poor countries as Mali and Burkina Faso to the coffee and cocoa plantations of the Ivory Coast.

As often as not, expulsions take place against a background of austerity imposed after a boom has gone bust. The current deportations from Nigeria fit that category.

Nigerian oil revenues have shrunk from $25 billion in 1980 to $10 billion, and the government, faced with an employment crisis and social pressures, has ordered illegal aliens lured by jobs to leave.

Ghana, a poor country, found it politically useful to deport the well-entrenched Nigerian community in the last decade, although the Nigerians had been here since both countries were British colonies.

In some cases, African governments have cracked down on non-Africans, including Europeans and Lebanese, who play an important role in industry and commerce.

As often as not the deportees -- the Lebanese at one end of the economic ladder and the Ghanaian laborers at the other end -- have found ways of returning and fulfilling an often economically useful, if politically exposed, function. Mindful of the seeming inevitability of further deportations, Benin, Ghana, Togo and Nigeria in January signed an agreement governing future expulsions in an effort to make them more orderly.

Under the agreement, the government expelling illegal immigrants would provide transportation to the border of the deportees' home countries.

Much of the confusion and violence surrounding the deportations from Nigeria stem from the failure of Nigerian authorities to honor that pledge.