The countdown to the Backstreet Boys' Las Vegas concert has begun, and the pop quintet's fans are having another manic attack at the MGM Grand Hotel. It has been an hour since their beloved Boys -- Howie Dorough, A.J. McLean, Nick Carter and cousins Kevin Richardson and Brian Littrell -- dashed through an alley entrance to shower and change before the show at the MGM Grand Garden Arena, but the hundreds of hysterical pubescent girls refuse to go away. "I love Nick!" shouts one. "For Nick, I'll die. If God says, `Die and let Nick live,' I'll do that."

Kids say the darnedest things. Especially those the Backstreet Boys keep running into on their 42-city summer tour, which ends Sept. 15 in York, Pa. Not since New Kids on the Block ruled the charts in the early '90s have five heartthrobs made so many girls swoon. "We like it," says Brian, 23, of the hoopla. "What guy wouldn't want a bunch of screaming girls around him?" The decibel level began rising last summer with the release of Backstreet Boys, their U.S. debut album, which has gone on to sell 6 million copies and produce four hit singles, including the No. 2 smash "Quit Playing Games (with My Heart)." No doubt the hysteria will be on view at the Sept. 10 MTV Awards, where the group, nominated for best group video and best dance video, will perform. "The Backstreet Boys may not be the best singers or dancers," says Seventeen music editor O.J. Lima. "But they use all the tools they have to the nth degree."

Actually, the Boys' popularity can be downright dangerous. During an Aug. 18 show in Edmonton, Alta., more than 50 fans were treated by paramedics after a horde of people surged toward the stage. Amazingly, many injured fans came back for more. "I was in tears because I was happy," says Heather Tasko, 13, who escaped with bruised ribs. "I was lucky to even get close to the stage. It was the best day of my life." Keeping one's cool when the Heathers of the world are losing theirs isn't easy, but the Boys try. "It's like having a split personality," says A.J., 20. "Onstage, I try to be as stupid and crazy as possible. Offstage, you try to act as normal as you can."

In Vegas, normal means kicking back in a complimentary $2,000-a-night, 6,000-square-foot penthouse at the Grand. The suite provides sanctuary, so leaving it to explore the city after the show could be tricky. Nick, 18, would happily end the evening with his beloved Nintendo, but A.J. hopes to check out Siegfried & Roy's magic extravaganza, while Kevin wants to go clubbing. First, though, he has to round up hotel security to ensure his safety and whisk him through a private entrance into the VIP room. But who's complaining? "We're having an incredible time," says Kevin, 26. "Here we are in a suite two stories high, and we're chilling."

Backstreet life hasn't always been so cushy. Last November the group faced its first -- and so far, only -- major crisis when doctors discovered that a congenital hole in Brian's heart had enlarged to dangerous proportions. With medical approval, Brian postponed open-heart surgery until May to meet touring obligations. The week before the surgery, Brian "was holding a lot inside," says A.J. "It wasn't a good dinner topic." Though worried about his best friend, Nick tried to remain upbeat: "I couldn't picture life without him. Thank God everything turned out the way it did." (The operation was successful.)

Brian remembers the days leading up to the operation very well. "I told my mom a lot of things that I never had the courage to say," he recalls. "I was telling her to take care of my dad." After spending eight weeks convalescing, Brian returned to the group in July, but paramedics still stand by during concerts in case he needs oxygen. The ordeal is the second close call for the Lexington, Ky., native. When he was 5, an infection caused his heart to stop beating for 30 seconds. "I wasn't supposed to live long," he says. "And I did. I look at that as a miracle. I've been singing ever since."

He joined Backstreet Boys in 1993, the year that A.J., Howie and Nick formed the group and began performing at Backstreet Market in Orlando. Kevin, who had moved there from his hometown of Lexington after his father's death from colon cancer in 1992, hooked up with the others through a mutual friend and recruited Brian. "We did a couple of small tours before anybody knew who we were," says Kevin. "We were staying in dives everywhere, but we didn't care. We were just getting crazy onstage."

That wild abandon paid off after they were signed by Jive Records in 1994 and quickly became a sensation in Europe before taking off in the U.S. last year. Yet for all their onstage magnetism, each Boy is blissfully unattached (except for Brian, whose actress girlfriend lives on the West Coast). "I meet so many interesting and beautiful women out on the road," says Kevin. "It's hard for me to say to a girl that I'm going to be faithful and not go on dates. I want to have a good time."

Others want to have a good fallback position. Howie, 24, has begun developing Florida condos in case the group winds up a one-blockbuster wonder. "We're not anywhere close to millionaires yet," he says. "But what we have made I'm trying to be wise with. "Still, there's that occasional urge to splurge. Howie recently purchased a purple Corvette Stingray, and Brian bought a house in Orlando last March. (The rest of the group live in the Orlando area.) Sometimes, though, it's the little things that keep them amused, like getting escorted out of the Grand for their night on the town by a hotel security team. "It was cool," says A.J. "You would have thought Elvis was in the house."