Saturday is the final day immigrants can apply for green cards under a government amnesty program.
Lawyers estimate as many as 100,000 immigrants may be eligible under the 1986 Immigration Reform and Control Act.
The legislation said people who left the United States between 1982 and 1987 could not be granted residency. About a quarter of a million people had their applications rejected. But many of them stayed in the United States anyway. Two class-action lawsuits challenged their disqualifications, and last year the cases were settled. Those immigrants have been allowed to apply for residency since last May.
Groups opposed to illegal immigration said the problems surrounding the 1986 program prove such initiatives don't work.
But supporters of broad immigration reform said granting residency motivates immigrants to educate themselves and contribute to society.