Underemployment in its most insidious form -- a dearth of meaningful career challenges -- is a long-standing problem for millions of American workers.

And in the 2000s, with job losses prevalent and legions held captive in positions that have gone stale, underemployment has become a critical cause of worker dissatisfaction. Here's why and what you can do about it.

The 'I'll Take Any Job' Syndrome

Suffering the slings and arrows of this unpredictable labor market, many laid-off professionals have been forced to take low-skilled jobs for a fraction of the pay and prestige of their former posts.

"Since the bursting of the Internet bubble, there are a lot of people existing on reduced expectations," says Howard Goldman, author of Choose What Works: The Proven Secrets to Professional Greatness.

After losing her job as a Web writer, Barbara Atkinson endured a year of low-wage underemployment before landing a contract gig as a multimedia specialist in the Boston area. "We have a huge workforce exceptionally well-trained to do tasks no one is asking them to do," she says.

A forced move into a new field usually means a cut in your standard of living.

"I can't think of any professionals who haven't taken a hit on salary," says Glen Wise, an engineer retired from Ciba Geigy, of the members of the Triad Job Search Network in Greensboro, North Carolina, which he advises.

What can you do if you've been knocked down several pegs in the new century?

• Keep up your credentials by continuing your education. Community college courses often provide high value. 
   
• Maintain your people skills and your presence in the community by volunteering or teaching in your area of expertise. 
   
• Keep your network healthy by pinging your contacts at appropriate intervals.

"A lot of hiring managers have sat in the other seat by now" and won't automatically dismiss a candidate who has endured underemployment, says Kay Nicolls, a human resources generalist with The HR Group in Greensboro, North Carolina. Working on contract after relocating with her husband, Nicolls considers herself underemployed.

The Underemployment-in-Place Syndrome

Can you become underemployed just by staying in one professional position for too long? You can, and in the 2000s, many employers have foisted underemployment on their workers by handing them ever-larger portions of the same work without granting them higher responsibilities.

Who's going to see to it that you rise to your potential?

"If you're an employee and you're looking for your manager to take care of you, you're making a mistake," says Beverly Kaye, coauthor of Love It, Don't Leave It: 26 Ways to Get What You Want at Work. These days, workers often must ask their bosses for work opportunities that will help them advance.

And there's more at stake than professional stagnation.

"If my salary keeps rising and I don't extend my skill set or take on new roles, at some point I'm going to economically eliminate myself in this position," Goldman says. "There's a young person or an immigrant who's going to take that job readily for half the money."

What can you do to keep yourself out of occupational quicksand?

• Get your work done efficiently, especially by delegating whenever you can. Then volunteer for projects that pull you upward. 
   
• If there's little upward mobility in your department or division, consider a lateral move within your company. 
   
• Move to a new employer if you must. If your job has kept your resume on a plateau for years, consider adding a skill through education or training. Marketers might study a language spoken in an emerging international market; IT pros could earn a state-of-the-art certification.

The Underemployment-by-Choice Syndrome

For a growing minority of professionals in the 2000s, downshifting is alive and well. Some workers choose to view their careers from a broader perspective.

"There's a certain percentage of professionals who have opted to be underemployed," says Smooch Reynolds, president and CEO of recruiter Repovich Reynolds Group in Pasadena, California. "We've seen a significant number of people rethinking their entire life strategy," especially since 9/11.

For the willfully underemployed, the question is: Can you stand the stress of risking your long-term career potential?