ISLIP, N.Y. -- As a high school varsity football player, Dennis Fleming waited impatiently for afternoon practice to end so he could sneak off and snort heroin.
After being expelled from school for assaulting another student -- "I split his head," Fleming said -- he indulged his appetite for drugs full time. He was arrested several times for burglary and car theft, spent a Christmas in jail and drove his mother to the brink of despair, all for the sake of his next fix.
Fleming is one of a small number of suburban teen-agers who have become addicted to heroin after experimenting with it at increasingly younger ages.
"I knew what I was doing was wrong," Fleming, 18, said when he returned recently to East Islip High School to tell other students about his ordeal. "I felt suicidal. But the easiest way for me to deal with it was to run to my drug of choice."
Heroin use by teen-agers does not yet amount to a national epidemic. But the average age at which heroin users first try the drug has been dropping in the last decade for several reasons, drug treatment specialists and law enforcement officials say.
Heroin is easier than ever to find. Its falling price puts it within reach of a teen-ager's allowance. Its unprecedented purity allows users to avoid using needles and to snort it. And its popularity, sociologists say, has shifted from the inner city to the suburbs, where few teen-agers have witnessed the damage that heroin can do.
Teen-agers are still more likely to use alcohol and marijuana than heroin. "It may have more the quality of a fad than anything else," said Dr. David F. Musto, a medical historian at Yale University. "There isn't the atmosphere supporting heroin use that there was in the late '60s and early '70s."
But the problem has produced overdoses and arrests in suburban pockets around the country, from New York to Delaware, Florida and Texas.
Although popular culture has been blamed for making heroin look glamorous to adolescents, drug treatment specialists call such an explanation simplistic.
And more than a few parents have been deceived into thinking that their children could not possibly be using heroin because they do not look like addicts. Dennis Fleming's mother never expected him to wind up addicted, she said, because he played Little League baseball for so many years. "I was never ever aware he had done heroin," Christine Fleming said. "I didn't know the symptoms."
Heroin's attraction for adolescents has little to do with personality traits, said Dr. Mitchell S. Rosenthal, a child psychiatrist who is president of Phoenix House, a nationwide network of drug treatment programs.
"It's easy for us, as we get older, to forget how powerful peer pressure is and how needy kids are to have friends and the acceptance of their friends," Rosenthal said. "If they are pained and drugs are available, and if they fall into a peer group where drugs are the currency, it's really going to stack the deck against them."
When Fleming and nine other adolescents from Long Island discussed their heroin addictions in a series of interviews, they said they were not lured astray by music or other pop influences.
The teen-agers, who were undergoing drug treatment at Phoenix Academy, a program run by Phoenix House in Ronkonkoma, N.Y., and at Outreach Project in Brentwood, N.Y., blamed stress in school or at home for their heroin use. "I felt it was easier to handle the pressure when I was high," Fleming said.
Most of them, in answering questions, said they came from broken or troubled homes, lacked self-esteem or felt depressed, and craved acceptance.
"I felt what I was doing was the cool thing, to hang out with my crowd," said Fleming, whose addiction landed him in treatment at Phoenix Academy.
Some teen-agers reported finding heroin for sale alongside the designer drug Ecstasy at raves -- all-night underground dance parties. "I was going to underground raves," Fleming said. "It would be like a real zombie fest."
Several teen-agers admitted that they did not like heroin at first, but feared balking in front of their friends. When Michael Nevins, 17, of Lindenhurst, was introduced to heroin on his 13th birthday, he recalled, "I was throwing up all over the place."
Heroin is plentiful around New York, law enforcement officials say, because it is funneled by Colombian traffickers who undercut Asian suppliers by offering a purer product. The high purity has enticed adolescents who flinch at the notion of pricking a vein with a needle, but will sniff heroin under the misconception that breathing it into their lungs is less addictive.
Dr. Herbert D. Kleber, medical director of the National Center on Addiction and Substance Abuse at Columbia University, estimated that at least half the sniffers wound up injecting heroin as tolerance developed for it. "There's a myth out there that you can't die and you can't get addicted if you're snorting," Kleber said.
With heroin cheaper than ever, users say, a bag supplying a single potent high averages about $10, or less than the cost of a movie ticket with popcorn.
"The lifestyle goes on and people don't see it," said Megan, a baby-faced 16-year-old who spoke on the condition that her last name and hometown be withheld.
Megan was 14 when she started sniffing heroin because, she said, "a lot of people that I know got high and they looked like they were enjoying it."
Before she turned 15, Megan said, she was skipping school and consuming six to eight bags of heroin a day. Even in treatment at Outreach Project, she found it hard to see herself as an addict.
"When I think of a real junkie, I think of somebody sitting in a corner with a needle in their arm," Megan said.