SAN FRANCISCO -- A recent meeting of the People With AIDS Coalition began, as it usually does, with a round of introductions. Each of the three dozen men seated in a semicircle in the chilly sanctuary of a church in this city's predominately gay Castro district gave his name, the date of his diagnosis and the infections he had endured. Last to speak was a slender, youthful-looking playwright who has become something of a local legend.

"Well, it's nice to be here," said Dan Turner, as the group erupted in knowing, appreciative laughter.

In this city most closely identified with the AIDS epidemic, Turner is famous for one reason: six years after being diagnosed with AIDS, he is still alive.

That means he has beaten phenomenal odds. Although many AIDS patients are living longer because of earlier detection and better treatment, most die within 18 months of diagnosis. A recent study of New York City AIDS patients estimated that they have about a 5 percent chance of living longer than five years.

Turner was one of the first 30 people here to contract AIDS -- there are now more than 5,000 people in San Francisco with the disease -- and is believed to be among the longest American survivors. When he was diagnosed Feb. 12, 1982, he was told he had "gay cancer," a mysterious new disease that seemed to single out homosexual men, killing most within a matter of months. Treatment was largely nonexistent and the disease that would be known as acquired immune deficiency syndrome had not been named.

"I thought I'd be dead in two months," recalled Turner, who recently celebrated his 40th birthday. In the insular world of AIDS doctors, researchers, activists and patients, Turner is a celebrity, one of the best-known survivors whose longevity and relative good health have inspired badly needed optimism and hope.

The physical and psychological characteristics of long-term survivors like Turner are being studied by the federal Centers for Disease Control (CDC) in hopes of discovering clues about the behavior of the virus. The CDC defines long-term survivors as those alive three years after diagnosis.

When the CDC began its study in December 1986, researchers obtained the names of 589 people diagnosed before December 1983 who were believed to be still alive. According to principal investigator Ann Hardy, epidemiologists discovered that more than half had died and 25 percent could not be located. Of the 99 who were alive and could be contacted, 26 have been enrolled in the study.

Survivors appear to have little in common except their initial infection with Kaposi's sarcoma, an otherwise rare skin cancer seen among gay white men with AIDS. "They tend not to quickly develop the other infections like pneumocystis pneumonia that kill people with AIDS," Hardy said. "Right now, we don't know why that is."

Living with AIDS requires profound adjustments, according to interviews with a dozen survivors. Although treatment varies greatly -- some people with AIDS turn to holistic medicine, others to black market experimental drugs, still others to conventional therapies -- survivors share a fierce determination to keep on living and an outlook that is hopeful yet realistic. Most have close friends or supportive families and some find solace in the religion of their childhood.

All say they have made an uneasy peace with uncertainty and anxiety. "Having AIDS is something I never forget," said Andrew Small, a former legal secretary here who was diagnosed 5 1/2 years ago, "but I certainly don't think about it all the time."

Many are deeply suspicious of organized medicine but express great faith in their own doctors. Some survivors are outspoken about their illness and have helped establish AIDS organizations that have provided the bulk of educational programs and support services. Others are intensely private and say they fear that talking about their longevity will jinx what they regard as inexplicable -- and undeserved -- good luck.

Several say they feel guilty, an emotion common to those who survive airplane crashes or other catastrophes.

"Everyone I took Suramin {a highly toxic experimental drug} with is dead, everybody I was in support groups the first two years is dead," said Stephen Pieters, 35, a Los Angeles minister who is approaching the four-year anniversary of his diagnosis. "It's spooky in a way, because I wonder, why me? I relate a lot to the Jewish writers who survived the Holocaust."

John Lorenzini, 40, who was diagnosed in October l983, compares living with AIDS to his 1968 tour in Vietnam, where he was a military diver.

"I don't have survivors' guilt," said Lorenzini, who helped launch Utah's AIDS program and now works for the AIDS Program of the East Bay in Oakland. "I was in a war and everything seemed surreal to me, and I think that kind of prepared me for what I've been going through. Sometimes I think my activism is my acting-out of grief, trying to make a difference."

Small says he is able to see some good from his experience with AIDS.

"Remember that old game, what would you do if you had six months to live?" he said. "I always thought I'd get so depressed I'd kill myself. But what I've found is that I just didn't give in to it, and that has been a major surprise to me, that I'm so strong emotionally."

Turner said he believes he was infected during a sexual encounter on a trip to New York in June l981, the month the disease was first identified. Several weeks after he returned home, he developed a yeast infection on his eyelid. By Christmas 1981, he noticed two small painless purplish spots above his right ankle that resembled cigarette burns.

In February 1982, when the spots seemed to be getting bigger, Turner consulted a dermatologist who performed a biopsy. The test showed he had Kaposi's.

"I was stunned," Turner recalled. "I didn't fall on the floor or scream. Physically I felt fine and I thought, 'Well, people survive cancer.' I was determined that I was not going to let myself fall apart."

In April 1982, he began experimental treatment with massive doses of alpha interferon at San Francisco General Hospital, where he was the second patient diagnosed with AIDS. The treatment halted the spread of his lesions.

Turner is a medical anomaly. Dr. Jay Levy, a San Francisco researcher who was among the first scientists to identify the AIDS virus, has been studying him for several years. Levy said he believes that Turner's longevity may be due to a subset of lymphocytes -- infection-fighting white blood cells -- that appear to halt the replication of the virus in his body.

Shortly after he was diagnosed, Turner decided he would not rely strictly on conventional medicine. Convinced that his mental state could affect his immune system, Turner decided he needed to take steps to reduce stress.

He consulted an acupuncturist and began meditating, both of which helped him relax. For several months, he took massive doses of vitamin C in the hope that it might boost his immune system. He continued his daily weight-lifting regimen, avoided alcohol and switched to a natural foods diet.

Turner receives $810 per month in payments from a disability insurance policy and other benefits, a sum that has enabled him to stay in the rambling three-story Victorian house he shares with two cats and five roommates, four of whom have AIDS or a generally less severe form of the disease known as AIDS-Related Complex (ARC).

In 1985, he decided to enroll in a master's degree program in social work at San Francisco State University. He continued to write musicals, several of which have been produced by community groups, and felt well enough that year to run five miles of the annual Bay-to-Breakers marathon.

"After three years, I felt I was over the hump," he said.

His longevity and his freedom from disfiguring or debilitating disease has awed and, sometimes, angered his friends with AIDS. "I remember visiting one friend who had toxo {toxoplasmosis, a parasitic infection of the brain that causes neurological damage} who said, 'Dan, why are you so healthy and I'm not?' " he recalled sadly. "I didn't know what to say to him."

Last year, Turner's equanimity was shattered. One by one, his old friends with AIDS, many of them early activists here and in New York, died. "I've almost been wiped out of my friends," he said.

Four months ago, Turner began displaying symptoms that alarmed his doctors. He lost 15 pounds and developed a persistent, unexplained cough. Blood tests showed that his T-cell count, which measures white blood cells that fight infection, was 144, far below normal. Two months ago, Dr. Paul Volberding, his physician, recommended that he start taking AZT, the only federally approved drug to treat AIDS. Turner, worried that it might "undo" whatever was keeping the virus at bay, reluctantly complied.

Although Turner has started to regain some of the weight he lost, he knows his health is declining. "At one time, I thought I'd live to be 70, that I could beat this, but I don't think that anymore. Even though my cancer is in remission, the virus has been eating away at my system, and there has been a general decline in my blood status. The truth is, I'm a sitting duck for other infections."

No matter how long he lives, Turner hopes his experiences will help others who have AIDS. "People always ask me, what do you do? Like there's some sort of secret, a reason that I'm still alive, which of course, there isn't. I want the public to know that there are people like me out there."