Most Americans can be hired or fired at the whim of employers as long as they are not illegally discriminated against. But what is discrimination?

QI work in marketing for a large environmental nonprofit. My boss requires her female staff to wear makeup, makes tactless comments about her preference for "young, pretty and thin," and uses euphemisms like "not contemporary enough" and "not our image" to reject older, heavier, less stylish or culturally diverse candidates. When I voiced the widely shared concern to human resources that such practices might be unethical, if not illegal, I was told it is acceptable to consider "image" in hiring and retaining marketing staff -- even those who have no contact with the public. A recent layoff seems to have allowed my boss to do some "aesthetic cleansing." As one of the few over-40 faces left, I fear my head will be on the chopping block next. Since HR has turned a deaf ear, can you clarify what is discrimination and how to challenge it?"

AMarcia Greenberger, co-president of the National Women's Law Center in Washington, said: "Employers can require dress and appearance which are consistent with professional standards. They cannot cross the line into discrimination" that violates various federal laws banning bias based on a person's age, national origin, race, sex, religion or disability.

The worker's complaint raises "lots of red flags," she said. "There are indications that the line has been crossed," particularly by the supervisor's saying she wanted "young" workers (possible age discrimination) and rejecting culturally diverse job applicants (possible ethnic or race discrimination).

Greenberger said the employee ought first to try to solve the problem internally, perhaps with a group of like-minded workers who could again approach the human resources department. "A number of employees may get a different response" than she did as an individual, Greenberger said. If that fails, they could file a complaint with the federal Equal Employment Opportunity Commission or perhaps a state or local human rights agency.

"Companies can't retaliate, either" against those who file complaints, she said.

-- Kenneth Bredemeier

E-mail your workplace questions to Kenneth Bredemeier at bredemeier@washpost.com. Discuss workplace issues with him Wednesday at 11 a.m. at www.washingtonpost.com/liveonline.