Routinely, his gray Toyota hybrid is parked from 6:30 a.m. until late at night outside Building 31 at the National Institutes of Health in Bethesda. Sometimes his colleagues leave notes on the windshield that say things like, "Go home. You're making me feel guilty."

But Anthony S. Fauci has made a career of long hours, exhaustive research and helping the public understand the health dangers stalking the planet. As director for 23 years of the National Institute of Allergy and Infectious Diseases at NIH, his milieu is the stuff that scares the daylights out of most people: bioterrorism, deadly flu epidemics, the enduring specter of AIDS.

Fauci, who is equally at home in the laboratory, at a patient's bedside, at a congressional hearing or on a Sunday morning talk show, scarcely has time to collect all the accolades that come his way. But this has been an extraordinary year. In the spring, he won the Kober Medal, one of the highest honors bestowed by the Association of American Physicians. In July, President Bush awarded him the National Medal of Science. And today, he receives one of medicine's most prestigious prizes, the $150,000 Mary Woodard Lasker public service award, as "a world-class investigator" who "has spoken eloquently on behalf of medical science," according to the Lasker Foundation.

No one deserves the honors more, his associates agree.

"Dr. Fauci is the best of his kind," said former U.S. surgeon general C. Everett Koop, 90, who has often sought Fauci's medical advice and counts himself as a friend.

For someone else, this might be heady stuff. But Tony Fauci, 66, has never strayed far from his down-to-earth Brooklyn roots or his Jesuit training, with its emphasis on service and intellectual growth. Beginning his career in the lab -- viewed by many as a backwater of medicine -- he soon became the chief detective probing a mystery that would encircle the world. Before AIDS even had a name, he made the "fateful decision," he said, to make it the focus of his research.

"It was a matter of destiny, I think, but by circumstance alone I had been trained in the very disciplines that encompassed this brand-new bizarre disease," he said. "This was in my mind something that was going to be historic."

He and his researchers would make breakthroughs in understanding how HIV, the human immunodeficiency virus, destroys the body's immune system. Years ago, he assumed a public role, calmly explaining the latest health scares on talk shows such as "Face the Nation." Through four presidential administrations, he has led efforts that resulted in Congress dramatically increasing funding to fight AIDS.

Today, as Fauci helps direct the president's emergency plan for AIDS relief in Africa and elsewhere, he also is leading the fight against such infectious diseases as anthrax and tuberculosis. In his $250,000-a-year position, he oversees 1,700 employees and a $4.4 billion annual budget.

"Fauci doesn't sleep," said Gregory K. Folkers, his chief of staff. "He's the hardest-working person you'll ever encounter."

The doctor's curriculum vitae supports that assertion. The bibliography alone is 86 pages, listing 1,118 articles and papers he has written or contributed to. (An example: "The Role of Monocyte/Macrophages and Cytokines in the Pathogenesis of HIV Infection," published in "Pathobiology" in 1992.) He has given more than 2,000 speeches, rehearsing with a stopwatch to whittle down his remarks. He has received 31 honorary doctoral degrees.

Vacations are seldom on the agenda. Often, his wife and three daughters accompany him to events. This summer, it was the International AIDS conference in Sydney. But he is seldom found sitting by the pool behind his Northwest Washington home. And retirement, he said firmly, is "not on the radar screen."

Exceptional Child

He learned to question early.

It didn't make sense to him when the nuns at his school said that you had to go to church to get into heaven. His beloved paternal grandfather, an immigrant from Sicily, spent his Sunday mornings cooking. What about him?

"I remember going up to him one day. 'Grandpa, why don't you go to Mass?' And he said: 'Don't worry about it. For me, doing good is my Mass,' " Fauci said.

The experience made him determined to do good through his work. He was 7.

The Faucis lived in the Bensonhurst section of Brooklyn, above the family drugstore operated by his father, Stephen, a pharmacist.

Fauci's only sibling, Denise Scorce, recalls that he was a well-rounded kid who liked to play ball but only after he did his homework.

"He was very normal in every way, but you kind of knew he was special," said Scorce, 69, a retired teacher who lives in Northern Virginia. "Everything he did was perfect."

Fauci won a full scholarship to Regis High School, a Jesuit institution in Manhattan. Later, he enrolled in another Jesuit school, the College of the Holy Cross in Worcester, Mass.

"The Jesuit training is wonderful. I don't think you can do any better than that," he said. "I always quote, 'Precision of thought, economy of expression.' "

Although he had an aptitude for science, he received his 1962 bachelor's degree in Greek/pre-med. He took the minimum number of science courses required for acceptance at Cornell University Medical College.

"I was very, very heavily influenced by the classics and philosophy, which I think had an important part in my ultimate interest in global issues and public service," he said. "I was interested in broader issues." I always tried to look at things at 40,000 feet as well as down in the trenches."

Encounter With ACT UP

One of the most dramatic episodes during Fauci's tenure at NIH occurred in 1989, when angry ACT UP demonstrators swarmed his building, demanding to be heard.

Fauci, like many top government officials, was accused of not doing enough to fight AIDS. The tactics were attention-getting: smoke bombs, staged "die-ins," chalk bodies drawn on sidewalks.

"He was public enemy number one for a number of years," said writer and activist Larry Kramer, who led the charge. "I called him that in print. I called him very strong, hateful things. . . . But Tony was smart enough to sit down and talk with us."

Fauci read the leaflets the group distributed and others threw away. "If you put it in the context of they were human beings who were afraid of dying and afraid of getting infected and forget the theater, they really did have a point," he said.

When police officers moved to arrest the protesters, Fauci stopped them. He invited a small group to his office to talk.

"He opened the door for us and let us in, and I called him a hero for that," Kramer said in a telephone interview. "He let my people become members of his committees and boards, and he welcomed us at the table. You have to understand that he got a lot of flak for that."

It was worth it, Fauci said. "That was, I think, one of the better things that I've done."

Doctor as Family Man

Christine Grady still laughs when she recalls her first meeting in 1983 with the famous Dr. Fauci. An AIDS nurse who had recently joined the NIH after working in Brazil, she was summoned to interpret for a Brazilian patient who wanted to go home.

Grady was dismayed when the patient responded to Fauci's detailed instructions on aftercare by saying in Portuguese that he intended instead to go out and have a good time. She knew Fauci tolerated no nonsense.

"He said he'll do exactly as you say" is how she translated the patient's remarks.

She thought she had been found out a couple of days later when he asked her to come by his office. Instead of firing her, as she feared, he asked her out to dinner. They were married in May 1985.

The Faucis live in an renovated 1920s home in the Wesley Heights neighborhood. Grady, 55, has a doctorate in philosophy and ethics from Georgetown, and she heads the section on human subjects research at the NIH's Department of Clinical Bioethics. Their children are also busy. Jenny, 21, is a senior at Harvard University; Megan, 18, who will attend Columbia University next fall, does community service teaching in Chicago; Allison, 15, is on the cross-country team at National Cathedral School.

"He's a goofball," said Jenny Fauci of her father. "He works hard and he does his thing, but he comes home and he's singing opera in the kitchen and dancing around."

She thinks she understands what motivates him. "Work is not really work for him," she said. "It's what he believes in."

And so Fauci will leave for the office before dawn and return home long after sunset. It reminds him of that speech he gave this summer at the AIDS conference in Sydney. "It was called ‘Much Accomplished, Much Left to Do,’ " he said.