Health care analysts say never judge health insurance by price alone. But an increasing number of government employees and retirees have signaled that they are willing to switch insurance plans when they think premiums are too high.

Officials who oversee the Federal Employees Health Benefits Program said they have seen more "migration" by enrollees than usual when premiums have jumped sharply in some plans. Officials also noted that plans that have held the line on costs -- such as the Blue Cross and Blue Shield Association's basic option and the Government Employees Hospital Association's standard option -- have seen enrollment grow.

For 2006, about 80 percent of FEHBP enrollees will see their premiums rise between 2.5 percent and 15 percent, officials said. The average premium increase is 6.6 percent, the smallest rise in nine years.

The FEHBP "open season" begins today and runs through Dec. 12. The program will offer 279 choices -- 11 fee-for-service plans and an array of health maintenance organizations -- next year. Some plans will cost enrollees less, and many will cost more.

The variation in cost makes it worthwhile for government employees and retirees to spend time studying their health plan's brochure, comparing plans and checking premium costs. Experts say some FEHBP enrollees can save hundreds if they are willing to shop around for a health plan.

"There are a lot of options out there. That is the big news," said Walton Francis, an economist who helps write the annual guide to FEHBP for Washington Consumers' Checkbook. "And it behooves people to do some homework."

Of course, it's not easy to switch health insurance, especially when favorite doctors and convenient hospitals are involved. Four fee-for-service plans, for instance, have developed a loyal following in FEHBP over the years.

The Blue Cross and Blue Shield benefit plan has more than 2.2 million enrollees -- 56 percent of FEHBP enrollment. The Mail Handlers benefit plan has more than 257,000 enrollees; the GEHA benefit plan has more than 228,000 enrollees; and the National Association of Letter Carriers benefit plan has more than 101,000 enrollees, according to the Office of Personnel Management.

The four plans offer a snapshot of how premiums vary in FEHBP next year.

The employee share of the premium for Blue Cross and Blue Shield's basic option, which provides no coverage outside the Blue network, remains unchanged from this year. GEHA also is not raising its rates for its standard option.

The employee share of the premium for Blue Cross's standard option is increasing by about 14 percent in 2006, and employee premium costs for the Mail Handler standard option will rise by 2.4 percent for individuals and 8 percent for families next year. The Letter Carriers plan, which provides only a "high" option, will increase employee premiums by 8.2 percent for individuals and 9 percent for families next year.

Most FEHBP plans cover the essential services, such as hospital and doctor care, prescriptions and outpatient lab tests. Because FEHBP provides a generous prescription drug benefit, federal retirees will not need to sign up for the new Medicare Part D drug benefit, OPM officials said.

Still, employees and retirees will want to check whether co-payments for brand-name drugs are increasing, whether colonoscopies and other preventive care screenings are covered and whether more visits are allowed to certain specialists.

Francis said several HMOs, such as Kaiser Permanente, Aetna and MD-IPA, "rate the highest in terms of the bang for the buck." Blue Cross basic, GEHA standard and the American Postal Workers Union consumer-driven option offer substantial cost savings when compared with some national plans, including Blue Cross standard, he said.

As in recent years, learning about the FEHBP options is easier for people who have access to the Internet.

OPM's health care portal allows employees and retirees to link to different Web pages and compare plans by Zip code, see premiums and find explanations for newer options, such as high-deductible plans with a health savings account.

Employees also can check on the OPM site to see whether their agency subscribes to two popular online programs -- Consumers' Checkbook and PlanSmartChoice -- that can be used to compare FEHBP plans and premiums.