In the 1970s, preferred-provider organizations (PPOs) began changing the rules of fee-for-service care. PPOs steer employees to cooperating doctors and hospitals that have agreed to a predetermined plan for keeping costs down. A PPO is similar to an HMO, but you pay for care when it is received rather than in advance.

If you have PPO coverage, you agree to use providers that your insurer and employer have contracted with at discount rates. Some plans require you to select a primary care physician, who can refer you to specialists. But others let you choose any doctor you want, including specialists.

You even can see a doctor who isn't a member of the PPO, but you'll pay the difference between the nonmember's bill and the PPO's discounted rate. Even if your nonmember doctor accepts the PPO rate, your plan may make you pay extra simply because he or she is not a member of the plan.

Because a PPO usually eliminates or reduces deductibles and co-insurance, joining could save you money if you stay with its list of approved providers. But a PPO could complicate a decision to use a specialist or facilities outside your home area. Check any such deals to make sure you're covered without a penalty if you get sick or injured in another town.

Health Maintenance Organizations When You're on Your Own