Facing a difficult economy and running short of ways to reduce health-care costs, employers are becoming more aggressive about checking the eligibility of their workers' dependents.

A Watson Wyatt survey of 489 employers this month for the National Business Group on Health found that audit reviews are the fastest growing change that companies are making to their health-care programs, well ahead of health risk appraisals or improving case management.

Susan J. Helke, practice leader for Watson Wyatt Worldwide's Group and Health Care consulting practice, said the trend is driven by companies' short-term need for cash and improvements in technology and administration that make the audits faster, cheaper and more effective. It's a matter of containing costs, meeting their fiduciary duty to monitor compliance, and simple fairness, she said.

"If you continue to carry people who are not on the plan, then costs go up for everyone."

The appeal of eligibility audits is that they almost guarantee hard-dollar savings -- with estimates of ineligible dependents typically in the 5 to 12 percent range -- and they often can pay for themselves within a year.

"We have completed dependent eligibility audits for over 50 employers and we have yet to have a case where the employer did not receive a return on investment of over 300 percent within one year. Many times it is well over 1,000 percent," said Michael Browning of Chapman Kelly, Inc., consultants in Jeffersonville, Ind. Mr. Browning, whose firm works with more than 25 Fortune 500 companies, said "demand during the first three months of this year has surpassed the demand during all of last year."

Pittsburgh-based Daniel Priga, a principal with Mercer consulting, said the firm "conservatively" estimates a $1,900 savings per year for every ineligible dependent taken off the books. Such a return "is hard to find in today's environment."

Mr. Priga said Mercer's audit numbers have doubled each of the past three years, from 50 to the current 200-plus nationally.

During an eligibility audit, employees are asked to document that family members on their health plans are eligible for coverage. They may be required to produce marriage certificates, proof of college enrollment or tax forms. Ex-spouses are not eligible. Nor are sickly uncles who live with the family. Stepchildren may not be eligible either, depending on the plan.

The single largest category of ineligibles, said Mr. Priga, are the 20-something children of employees who are not in school or have recently graduated. The error is usually inadvertent, he said, so it is a matter of educating workers about eligibility requirements. "Our results would not tend to show there is a lot of fraud going on."

For employees, the word "audit" rarely is welcome news. No one undergoing an audit expects to come out with more benefits, and the notion that the process might keep their premiums down may seem too removed to appreciate.

To lessen anxiety, companies often will offer an amnesty period, during which employees can voluntarily remove ineligible persons from their plan without fear of being hit with repayments of past claims. But there have been instances in which companies have fired workers for what they've considered violations of ethics policies.

If it sounds harsh to strip health coverage from a recent college grad, or someone dealing with chronic illness, two other findings from the Watson Wyatt survey are noteworthy: In the past three years, the companies involved say they have been less likely to raise employee copayments, increase employee premium contributions or restrict eligibility.

The trade-off, however, is greater vigilance in monitoring eligibility.

"Employers are considering, and implementing, dependent eligibility audits to assure that they are providing benefits to only qualified dependents and are not paying benefits for people who are not eligible," said Christine Whipple, executive director of the Pittsburgh Business Group on Health.

Last August, General Motors announced it would audit eligibility of workers' dependents to try to bring down its $4.6 billion health care bill.

A month later, New York State said it would do the same for the 1.2 million state employees. The expected savings no doubt will entice more to go the audit route.

Eventually, the trend toward more audits likely will flatten, Ms. Helke said, as companies improve the enrollment and administration of their health plans.

But for now, it is a quick and simple answer for finding immediate cost savings in a tough economic environment.