SAN FRANCISCO -- These days, Dr. Lorraine Day goes into her operating room in full protective gear. Two pairs of gloves, goggles, a face mask, double sleeves, double shoe covers, boots up to her knees. The chief of orthopedics at San Francisco General Hospital is trying to practice safe surgery. But she is scared anyway and not a little angry.

''Yesterday, I did five operations,'' says Day. ''Thirty percent of my patients are at high risk for AIDS. One of my patients recently needed 250 units of blood. It was pouring into him and all over us. They tell us to be careful. But as a surgeon you cut yourself many times. Would you tell a carpenter, don't cut yourself for the rest of your life?''

How frightened is this experienced surgeon about getting AIDS from a patient? ''Honestly?'' she asks and answers, ''I have to decide whether I want to continue in medicine.''

What angers Day and many of her quieter colleagues is that she has no right to know which of her patients carry the deadly virus. What bothers her further is that she has no right to refuse to operate, even minor elective surgery, on a patient with the virus.

It is not surprising that these concerns -- like the virus itself -- have hit first and hardest in San Francisco. But they are spreading as widely as the disease. Are doctors, nurses, expected to place themselves at risk every day without information? Are they legally or morally obligated to give AIDS patients the exact same treatment they would give others?

So far it is believed that only a dozen health workers -- including a technician here at San Francisco General -- have been infected on the job. Statistically, Hepatitis B, which killed 100 health workers last year, seems a much greater risk. But risks are not spread equally through the medical population. Nor are the feelings of risk. Day believes fervently,''It's only a matter of 'when,' not a matter of 'if.' ''

In another corner of this hospital, Dr. Molly Cooke, an internist, is familiar with this anxiety. The mother of three small children and wife of Dr. Paul Volberding, who cares for AIDS patients, went through ''absolutely excruciating anxiety, almost intolerable'' when she realized the nature of the disease to which she and her family had been exposed. But as an internist she tends to think of the reassuring statistics, while the surgeons tend to think case by bloody case.

Still, Cooke, like other doctors I spoke with here, is uncomfortable not knowing which of her patients carry the virus. Even Dr. Mervyn Silverman, president of the American Foundation for Aids Research, says, ''In the best of all possible worlds, physicians should know.'' He opposes mandatory testing for hospital patients because ''this knowledge has side effects that are disastrous.'' Among those side effects may be the refusal of medical treatment.

Should medical people be allowed to withhold care? The easy answer is a blanket no. It is unethical for a doctor to turn away someone who is sick. ''When you get your medical degree,'' says Dr. Silverman, ''it doesn't come with a limited warranty, only good for nonrisky situations.''

But there are times when the benefit to an infected patient may not warrant the risk to a physician. Should a doctor have to operate on a broken ankle rather than set it in a cast? asks the orthopedic surgeon. Should you have to perform a bunionectomy rather than prescribe a therapeutic shoe?

''If we lost a doctor for each AIDS patient,'' says internist Cooke, ''society might decide this is not how we want to spend our doctors. But the risk is lower. At some point we accept the loss of doctors to take care of hundreds of thousands of sick.'' But at what point and for what goals?

This horrific epidemic is still relatively young. Our statistics are raw. We are just beginning to deal with the real medical and ethical dilemmas.

If we are going to trust the health-care profession to treat the sick, part of that trust is to give it privileged information, the tools of the job. In an emergency, there is no time for an AIDS test. But when possible, a doctor should know whether a patient is infected. Some may abuse that information, some may refuse care. We'll have to depend on their professional ethics and pressure to minimize such breaches.

We must also reframe the arguments about treatment. It can't be cast simply as the patient's right to all care versus the doctor's right to any refusal. We need to assess more fully the benefit to a patient against the risk to health-care workers.

We are in this AIDS epidemic for the long haul. Those in the hospitals are taking risks; we expect them to. Tomorrow, Dr. Lorraine Day will operate on five more patients. If we want her and her colleagues to go on, we have to devise strategies that offer the profession what it offers patients: better care and better protection.