ONE OF THE HARDEST DECISIONS facing a young person with HIV is whether to keep the whole thing a secret.

"I knew I was going to wait until I graduated high school to tell my friends I was HIV positive," says Mark, a college student in New England. "I wanted to go through high school as a normal kid, and not as the boy with AIDS. I didn't want to get beat up and made fun of every day because I had AIDS."

Mark is 18, and grew up in a working-class neighborhood in Boston. A hemophiliac, Mark got HIV infection from contaminated blood products. His parents told him the news when he was 12 years old. After he cried, Mark went to the bathroom and vomited.

From that day on, Mark kept his illness a secret from even his closest school chums. When he needed to take anti-AIDS drugs during the day, he skulked off to the boys' bathroom to gulp down the handful of pills.

"We ended up giving him his afternoon medicine when he walked in the door after school," says Mark's mom, Diane. "It was just getting to be too hard on him."

Since graduating last spring, Mark repeatedly goaded himself to tell his friends about the disease. "But every time, I chickened out. I was scared and I just couldn't do it. I don't want to lose friends," Mark says.

Going to College and Going Public

Mark belongs to a tiny, but growing, fraternity: HIV-positive kids who are living long enough to attend college. When he arrived at the well-scrubbed campus of his small liberal arts college in New England, Mark pledged he would no longer conceal his illness. Initially, he planned to raise the issue simply by taking his medications in front of his three roommates, with whom he shares a cramped dorm room.

After all, it's hard not to wonder aloud why the guy in the other bunk quaffs a dozen pills each day. But Mark lives with guys who either discreetly mind their own business or simply lack curiosity; they never asked.

Finally, Mark told one of them, and the news spread. "There've been no negative reactions yet," Mark says, "which is good. It makes things a lot easier."

Because of HIV, Mark's never really had a major girlfriend - by his own choice. There have been opportunities, but Mark's decided, so far, to abstain from sex. "Before I even think of putting somebody at such a risk, I have to really, really love that person," he says. "But if I really love the person that much, how could I even think about putting them at that risk? If I were to ever give somebody HIV, it's pretty much like killing them."

One of Mark's close college friends, Natasha, doesn't deny that HIV makes for complications. In a recent conversation, she counseled Mark not to spill the news on a first date. "If you find a girl that's really your type," she said, "I think you should say something before anything gets intimate."

Mark smiled at her skeptically and asked, "What would be your reaction if, after a few dates with somebody, they told you they were HIV positive?"

Natasha replied, "I'd be like, 'Okay, what do we do now?' It depends on how serious the relationship was going. If we were planning on doing anything, we would have to just figure stuff out. It wouldn't be like, 'Oh shoot, I gotta run away now,' you know?"

Counseling programs for HIV-positive teens rarely seem to discourage their clients from having sex entirely. Instead, says pediatrician Cathryn Samples of the Boston Happens program, they explain how to have sex in the safest ways possible. "We never say to a kid that this diagnosis means you can never date, you can never have a relationship, you can never have children," Samples says.

Scientists says the risk of an HIV-positive mother passing the infection to her child is about 25%. Studies suggest that with anti-AIDS medicines, the risk can be reduced to 8% or lower. Samples says that about half of the young women she cares for have had children, including two teens who were born HIV-positive. Counselors at Boston Happens ask the young people to consider what it would be like to have a baby born HIV-positive, and to think about the fact that they may die long before the baby grows up.

These are issues, Samples says, that any couple with HIV has to face if they plan to have children. "But it's more complicated for teenagers, when they're still at the age of denying that these things are ever going to happen to you."

Focusing on the Near Term

While the burden of a childhood with HIV compels some young people to take heedless risks, others grow up more quickly than their peers. Like Mark, they seem more cautious and thoughtful than typical teens.

Mark hopes to have a family some day, especially a son. But he assumes he'll have to adopt, maybe even on his own. "It's hard for me to imagine someone who would want to marry a guy with HIV," he says.

Still, Mark keeps an open mind, and is telling more people about his disease. He even made a presentation about his disease in a speech class. After years of concealing this significant part of his life, Mark is relieved, and a little stunned, that it's not such a big deal to others.

Only a few years back, Mark doubted he would ever get to college. But with the help of the anti-viral "drug cocktail" he's on, Mark says college is looking like the best time in his life.

"People are no longer dying with HIV, they're learning to live with HIV," he says firmly. "The only thing holding people back from living with HIV is other people putting them down."