We will feel, we will think, we will talk about this case. But what will we do?

Our first reaction to the Supreme Court decision in the Cruzan ''right-to-die'' case is sympathy for the family. Nancy Cruzan, 32, lies in a persistent vegetative state after a tragic auto accident more than seven years ago. Her family has wrestled since then with her severe injuries, her condition, and the difficult decisions involved in her treatment. We may argue for years about which side ''won'' this case, but there are no victors on the personal level, only the certainty that the Cruzan family's suffering will not end with the Supreme Court ruling.

We will talk about these issues for a long time, at bus stops, in classrooms, in houses of worship. We may even casually discuss the case over breakfast with our families, and during breaks at work. We will mention to our friends and others that we wouldn't like to end up like Nancy Cruzan. Some of us would not want to endure the treatment she is being forced to endure. Others of us would want to make sure that our loved ones knew we would want such treatment.

But there is more to do than feel and talk. The court's decision, as well as a rash of subsequent news stories, has highlighted the usefulness of ''advance directives,'' such as living wills and durable powers of attorney. These are written indications of preferences that we may or may not already have casually discussed. They document how we would like to be treated, or who should make treatment decisions, if we should lose the ability to communicate.

The Missouri Supreme Court, ruling in the Cruzan case, held that ''no person can assume that choice for an incompetent in the absence of the formalities required under Missouri's 'Living Will' statutes or the clear and convincing, inherently reliable evidence absent here.'' This suggests that living wills constitute the kind of proof with which the court would be comfortable. Justice O'Connor wrote a concurring opinion that also highlighted the desirability of durable powers of attorney for health care. She wrote, ''These procedures for surrogate decisionmaking, which appear to be rapidly gaining in acceptance, may be a valuable additional safeguard of the patient's interest in directing his medical care.''

So the most important practical lesson is this: There are ways to make our wishes about medical treatment known. Virtually all states have some form of advance directive legislation on the books. Forty states have living-will laws. Twenty-nine have laws that enable the appointment of a surrogate. And advance directive forms are easy to fill out; researchers at Harvard have found that a comprehensive form listing preferences for a broad range of medical treatments can be completed in less than an hour.

In spite of the usefulness and availability of advance directives, only about 9 to 15 percent of the population have filled them out. Why so few? Certainly, one major reason is our discomfort when dealing with issues surrounding death. However, I believe there are two other reasons: first, that people don't know about the opportunities their states have provided them, second, that health care professionals themselves don't know about advance directives. One study, for example, found that 23 percent of doctors are not familiar with living wills and 74 percent are not familiar with durable powers of attorney. Another study found that more than 60 percent of doctors are not familiar with their state's advance directive laws.

The Supreme Court has stated that people have the constitutional right to accept or refuse treatment. The irony of the Cruzan case is that people lose the capacity to make health care decisions just at times when some of the most important decisions need to be made. The Cruzan case teaches us that we can complement our thoughts and feelings with concrete actions that ensure that our medical treatment decisions can be known at times when we may be incapacitated.

At the federal level, legislation is already being considered to help all of us become more aware of ways to communicate our wishes more clearly. Sens. John C. Danforth (R-Mo.) and Daniel P. Moynihan (D-N.Y.) introduced the Patient Self Determination Act last October: I, along with a number of my colleagues, have introduced a similar bill in the House. The Patient Self-Determination Act requires health care providers to provide information to patients about advance directives and to educate their staff about these documents.

Our bill does not force people to fill out advance directive forms, nor does it limit the choices people can make. What it does do is help people get the information they need so that they can take positive action to avoid tragedy. This proposal has been endorsed by a broad range of medical, legal, religious and patient groups.

Knowledge is power. The Patient Self-Determination Act will empower people (and their doctors) to make good decisions by informing them of the options they have. Greater knowledge will lead to better communication among patient, families and doctors, and may avoid some of the heartbreaking cases such as Cruzan's.

The writer is a Democratic representative from Michigan and a member of the Ways and Means subcommittee on health.