Q. My husband is going to retire and his employer will no longer cover us under our current dental plan. I have been looking for a dental plan for retirees but haven't had much luck. Is there anything special I should know about these plans or somewhere I should check?

A. It will likely be very difficult to find dental insurance coverage aimed at retirees unless you sign up for a Medicare HMO that provides dental benefits. You may wish to check the HMOs that participate in Medicare in your area. An easy way to do that is to visit www.medicare.gov on the Internet, where you will find something called "Medicare Compare," which allows you to look at the HMOs that are available in your county and what extra benefits they offer. In some areas there are also companies that just offer dental insurance. This coverage, however, is likely to be limited to a list of participating dentists. Your own dentist might have suggestions if he or she participates in such a plan.

Q. My husband retired early and we have insurance through COBRA. We're having trouble finding a group to buy insurance from and since we are older, getting an individual policy is very expensive. Are there any remedies for us mature adults?

A. Once your COBRA coverage expires, your only guarantee is to be able to purchase some type of individual policy (with the rules varying depending upon the state in which you live). For older persons, the costs of this insurance are likely to be particularly high, however. You should shop around. Companies can vary dramatically in the amounts they charge and the options available to you. Generally, you can lower your costs if you accept a higher deductible in a traditional insurance plan or if you enroll in an HMO or other managed care plan.

Q. In January, the company I worked for ceased operations, but did not declare bankruptcy. However, it was behind on payments to our insurance company, even though they had collected premium money from the 125 employees. We're wondering how we go about trying to get a COBRA policy since the insurance company says it will not accept payments directly from the ex-employees?

A. Because COBRA is intended to offer extended insurance coverage through an employer plan, when that plan no longer exists (as in the case where the company has gone out of business), there is no insurance to offer to individuals. The insurance company is not obligated to continue that policy. You do have some rights, however, through the Health Insurance Portability and Accountability Act (HIPAA). Each state has to establish a way for people who had group coverage for at least 18 months before losing it to buy insurance on an individual basis. Unfortunately such insurance can be very expensive.

Q. You often write about Medicare Part B. What is Part A? Who is eligible for it and how do you qualify?

A. Persons who are legal U.S. residents and have continuously resided in this country for at least five years may buy into Medicare. That is, they will have to pay the full costs of Part A ($309 per month in 1999) and must also purchase Part B coverage ($45.50 per month in 1999).

Q. I am a senior citizen who has a green card. I don't get Social Security. I want to know if I can get Medicare.

A. For most people, Part A, Hospital Insurance, of Medicare is that portion of the program funded by your payroll taxes. Anyone eligible for Social Security benefits (as a worker or a dependent) is eligible for Part A on the first day of the month in which they turn age 65 or after a two-year waiting period after beginning to receive Social Security disability payments. Persons with end stage renal disease are also eligible at any age as long as they are insured workers or dependents of insured workers. You can also qualify for Medicare as a government worker. Those who are eligible for Part A in these ways do not have to pay the $309 premium for this portion of Medicare.

When you turn 65, if you are drawing Social Security benefits, you will automatically be enrolled in Part A. Otherwise, you need to apply for benefits through the Social Security Administration. Unless you decline enrollment, you will also be automatically enrolled in Part B, which covers the cost of physician and other outpatient services. Part B is voluntary and requires a premium contribution each month.

Do you have questions about health care coverage? Changes are occurring in the medical marketplace, and the debate over costs, quality and access to care continues. The Washington Post free telephone information service can take your questions. Call POSTHASTE at 202-334-9000 on a touch-tone phone and enter category code 8500 (in Prince William County, 703-690-4110). Economist Marilyn Moon of the Urban Institute provides answers in a periodic column.