U.S. companies are learning to deal with the increasing diversity in the American workforce, including accommodating a variety of religious customs. The issue has taken on heightened importance after the September terrorist attacks, and the ensuing backlash against Muslims in America, which, experts say, has also played out in the workplace.

A survey published last year by an interfaith study center said the number of religions represented in the American workplace has multiplied in the past five years, reflecting the increased diversity of the U.S. population.

The number of complaints of religious discrimination has also increased.

When a Muslim needs some time off every day for the required Islamic prayer, the U.S. law says the employer should accommodate those needs. When Jewish employees or Seventh Day Adventists says they cannot work on Saturday, the Sabbath of those religions, the law says the company should adjust their work schedules.

The 1964 Civil Rights Act requires employers to reasonably accommodate the religious practices of their workers, unless doing so would cause undue hardship on the employer.

David Frank is chief counsel for the Equal Employment Opportunity Commission. He recently told a Washington conference on religion in the workplace that distinguishing between hardship and inconvenience, harassment and intimidation is more complicated in practice.

Mr. Frank says religious discrimination cases represent only two percent of the total of work-related lawsuits filed by the EEOC. Until now, Mr. Frank says, the largest number of cases has involved workers fired for refusing to work on their Sabbath, or for wearing religious garb.

But, he notes what he calls a troubling increase in the number of discrimination cases filed by Muslim workers since the September 11th terrorist attacks. Nearly 500 cases of discrimination against Muslims have been filed since then, compared with fewer than 200 in the year prior to the attacks. "Worrying about how the public or your customers perceive an employee because of their religious garb is every bit as illegal as refusing to hire somebody because he is Black," he points out.

Sharifa Alkhateeb of the North American Council for Muslim Women blames the backlash on what she calls the "demonization" of Muslims. "There's an atmosphere of fear that makes people act in ways that are counter to what the laws allow," she says.

Looking at the broader issue of religious discrimination in the workplace, labor lawyer Larry Lorber of Washington says many small and medium companies complain that accommodating religious beliefs is costly. "What does one expect an employer to do when there are all the competitive requirements, the requirements to keep their businesses running 24 hours- seven-days-a-week?" he asks. "Are we expecting employers to get into the business of picking and choosing, triaging various religious beliefs, and accommodating one at the expense of another?"

Avi Schick of the New York District Attorney's office says employers need to be better informed about the law. "Employers need to be educated. Often, they want to be educated," he said.

Mr. Schick has recently published a book outlining federal and state laws governing religious and ethnic discrimination in the workplace that is being distributed to the business community.

Mr. Schick says employers need to understand that accommodating religious and ethnic diversity in the workplace would cost less than paying for a legal battle over discrimination, which they most likely would lose.