By MONICA DAVEY

In Bonita Springs, Fla., 10 restaurant workers were fired this week after skipping their shifts to attend a rally against legislation in Congress cracking down on illegal immigrants. In Tyler, Tex., 22 welders lost their jobs making parts for air-conditioners after missing work for a similar demonstration in that city.

And so it went for employees of an asbestos removal firm in Indianapolis, a restaurant in Milwaukee, a meatpacking company in Detroit, a factory in Bellwood, Ill.

In the last month, as hundreds of thousands of people around the country have held demonstrations pressing for legal status and citizenship for illegal immigrants, companies, particularly those that employ large numbers of immigrants, have found themselves wrestling with difficult and uncharted terrain.

They worry about how to keep their businesses operating, fully staffed, but also not to appear insensitive to a growing political movement that in many cases sustains their work force.

Some fired workers have complained that they were being singled out for their political views, and a few have filed formal complaints with the National Labor Relations Board. Other protesters have cut deals with their employers to work extra shifts in exchange for time off, or to close down their small businesses entirely, in deference to the sentiment behind the demonstrations.

In at least one instance, nearly 200 fired workers in Wisconsin were reinstated, demonstration leaders said, after the leaders met with employers, discussed the significance of the protests and threatened to identify the companies publicly.

"I have no problem with the demonstration, but this is a business," said Charley Bohley, an owner of Rodes restaurant and fishmarket in Bonita Springs, who fired the 10 workers there after posting a note warning employees that they could not miss work for a rally on Monday. "Couldn't they have protested in the morning before work? Couldn't they have protested in their hearts?"

Though the number of workers who have lost their jobs across the country, estimated in the hundreds, is small compared with the numbers marching in the streets, some protest organizers say word of the firings spread rapidly and might have a chilling effect on many more workers and on students, some of whom also say they have faced discipline for missing school for rallies.

The firings have also forced some organizers to rethink how best to plan future demonstrations, and some are considering opting out of events now in the works.

In Washington, Jaime Contreras, the president of the National Capital Immigration Coalition, said his coalition voted on Thursday night not to take part in a proposed national boycott or strike set for May 1. Jose I. Sanchez, an organizer in Texas, said his group was considering holding a rally on the Sunday before May 1 instead, just to avoid such strains.

"We shouldn't put our progress in jeopardy," Mr. Contreras said. "That is a tool you use when you have to, but you have to be completely prepared for backlash and repercussions."

In many cities, rally organizers said, plenty of businesses, many of which have pushed for efforts to give legal status to immigrants, cooperated with the demonstrations and allowed workers time off. In Indianapolis, one company went so far as to let 2,000 people leave their jobs for Monday's demonstration downtown, said Ken Moran, an organizer.

"The firings we've seen were an anomaly," Mr. Moran said, "but it's a sad situation."

In complaints filed with the government in one case, Mark A. Sweet, a lawyer for two fired restaurant workers in Milwaukee, said the restaurant had violated the National Labor Relations Act by firing the workers for what he considered legally protected activities: efforts to assist in the mutual aid and protection of themselves and other immigrant workers.

Other legal experts, however, questioned whether such a provision would apply to a public rally, and suggested that the workers had few remedies. For the most part, "at-will" employees may be fired at any time, for any reason, said Charles B. Craver, a professor at The George Washington University Law School.

"For private employers, there is normally no special First Amendment right to get out of work to engage in a protest," said Rodney A. Smolla, the dean of the University of Richmond School of Law. "A company might decide that it's good for morale to accommodate the exercise of freedom of speech on an issue that is very important to people, but that's an employment judgment not law."

In Tyler, Tex., Maria Rodriguez described on Friday how she and others had lost their jobs putting together equipment for air-conditioners for Benchmark Manufacturing Inc. Ms. Rodriguez, 32, who said she had made $6.75 an hour after several years with the company, said she had always been given time off in the past for personal appointments. This time, though, she was fired, she said.

"To me it seemed unfair," Ms. Rodriguez said. Even as she was being fired, she said, she saw applicants arriving at the company to replace her.

Benchmark Manufacturing issued a statement outlining the company's absence policy, and adding, "This issue is not about going to the rally, it is about following the company policies that govern every employee."

Against the backdrop of the broader immigration debate, the firings raised another tangled issue for some of the companies and for the workers: the legal status of those employees removed. Ms. Rodriguez, a native of Mexico, said she moved to the United States 14 years ago and did not have legal status. Some other advocates for those fired in other states said they did not know the legal status of the workers.

Elsewhere, after advocates intervened, some workers were rehired this week. At Wolverine Packing in Detroit, company officials said they invited 21 fired workers — 20 of whom were considered temporary workers — to return to their jobs, with back pay, on Monday. The company, meanwhile, issued a statement saying it planned to recheck employment documentation "due to reports that some of the temporary staffers may have been illegal."

Elena Herrada, who met with the company on behalf of the workers, said she did not know if any of them were in the United States illegally. The employees were already unhappy with their working conditions, Ms. Herrada said, and none were planning to return.

Gretchen Ruethling contributed reporting from Chicagofor this article.