Our hero, heroin.

KURT Cobain, the late lead singer of the breakthrough grunge band Nirvana, used to steal drugs from pharmacies when, at age twenty, he worked as a (listless and unreliable) janitor in Olympia, Washington. He became something of a connoisseur. Cocaine and speed, he later explained, weren't his favorites: ''I felt too confident and too sure of myself. Just too sociable.'' Not his style. Cobain's drug of choice, found in his bloodstream after he blew his head off with a shotgun in 1994, became heroin.

The supposedly impending heroin epidemic has been the subject of countless news stories in the last four years. By all accounts already under way among the tragically hip, the epidemic certainly makes great copy. Newsweek reports: ''The 31-year-old screenwriter looks like she's en route to a dinner party in her $300 dress.'' (Actually, that's heroin in her compact). One New York Times article begins: ''Even with her striking beauty, hardly anyone seemed to notice the young model as she glided through the swarm of heroin dealers and glassy-eyed addicts on a patch of steamy pavement in East Harlem.''

The numbers -- heroin-related emergency-room visits are up more than 150 per cent since 1990 -- do seem alarming, although it's always difficult to gauge where hype ends and reality begins when drug-starved models are involved. What's clear is that heroin is in our cultural bloodstream. The hit British novel and now film Trainspotting follows a group of Edinburgh smack addicts, one of a series of recent movies (including Pulp Fiction and Basquiat) to feature the drug. Yet another grunge rocker died of an overdose this July. And the bitter-almond smell of heroin is reportedly inescapable at hot Hollywood parties.

Drugs always reflect the era in which they achieve their vogue. In the late 1960s and early 1970s LSD was the emblematic drug. Its alleged power to raise one's consciousness appealed to the spiritual pretensions of the hippies and New Left. It was the drug of tuning in and dropping out, of passive revolt and keen self-awareness. The cocaine of the 1980s, in contrast, was a social stimulant, promoting aggressiveness and self-confidence. The protagonist of Jay McInerney's Bright Lights, Big City snorts cocaine whenever his energy flags at a downtown nightclub, refueling to continue the endless pursuit of good times.

The culture of heroin is different. When Mark Renton, the main addict in Trainspotting, and his mates take the drug, they fall back on the floor to enjoy their hit staring at the ceiling. It is a drug of isolation and oblivion (hence its appeal to the aggressively shy Cobain) -- and even pain. First-time users typically throw up. Heroin's needlework parallels the self-mutilating body-piercing now all the rage. And addicts experience excruciating pain, described in terms of muscles being ripped from bones, etc., if they don't feed their habit. The pointlessness of heroin, its invitation to oblivious solitude, and its danger make it the drug of grunge ''authenticity,'' tapping into a powerful current in today's popular culture.

Grunge, as articulated in 1990s ''alternative'' music (the mix of punk and heavy metal that is now the rock mainstream), is about feeling good about feeling bad. The lyrics celebrate failure and inadequacy. Cobain, the ur-grunge rocker, sang songs with lines like ''I think I'm dumb,'' repeated in a numb, flat voice. Sarah Ferguson of the Village Voice argues: ''The empowered feeling you [read: teenage white kid] get from listening to these songs lies in unearthing [an] essential nugget of shame.'' The songs let the listener sample and even enjoy his own perceived worthlessness, like pressing your tongue against a sore tooth. Grunge shares some qualities with the old 1960s counter-culture. It is hostile to the bourgeois and consumer culture. It is at the same time, like 1960s activism, an outgrowth of wealth and leisure (it's not easy to be a tortured victim of ennui working on a factory floor). But there are important differences. Grunge is for the most part shorn of ideals and the impulse for political action. Whereas 1960s student rebels were mostly the product of middle-class two-parent families, the defining family for grunge kids is the broken home, a consistent theme in their music.

When Kurt Cobain was eight his mother divorced his dad; she then lived with an abusive and unbalanced boyfriend, and then married a drinker and womanizer. ''I'm a product of a spoiled America,'' Cobain once said. ''Think how much worse my family life could be if I grew up in a depression or something. There are so many worse things than a divorce. I've just been brooding and bellyaching about something I couldn't have, which is a family, a solid family unit, for too long.'' The complaints about divorce do slip into whining, a victimology for white kids. And if the pain of divorce is real, the grunge solution is to revel in it, creating an upside-down world where isolation and inadequacy are virtues, and where a drug like heroin acquires a romantic cachet.

Trainspotting's Mark Renton, a character who suffers from vague, uncharted psychic wounds and who, like Cobain, despises the middle class, explains (in Scottish dialect) the appeal of heroin: ''Life's boring and futile. . . . We fill up oor lives wi s -- --, things like careers and relationships tae delude oorsels that it isnae aw toally pointless. Smack's a honest drug, because it strips away these delusions. Wi smack, whin ye feel good, ye feel immortal. Whin ye feel bad, it intensfies the s -- -- that's alredy thair. It's the only real honest drug. It doesnae alter yir consciousness. It just gies ye a hit and a sense ae well-being. Eftir that, ye see the misery ae the world as it is, and ye canae anaesthetise yirself against it.''

Heroin saves Renton and his pals from worrying about the daily routine -- ''bills, food, bailiffs, these Jambo Nazi scum beatin us, aw the things that ye couldnae gie a f -- -- aboot whin yuv goat a real junk habit.'' But it's the nature of pop culture that such an anti-bourgeois protest immediately gets caught up in the everyday consumerism it reviles. Tortured grunge bands become instant commercials on MTV -- and get very rich. On the TV show The Simpsons, a member of the band Smashing Pumpkins tells the suburban dad Homer Simpson that he envies his simple domesticity -- because all the band has is hordes of adoring fans, millions of dollars, and its youth. Even Cobain's suicide, supposedly motivated in part by disgust with success, has become a sort of posthumous stage stunt and marketing gimmick.

Authenticity, when it is equated with a stance against the world --and especially once it becomes hip -- invites posing and self-deception. A friend of Renton's tells him: ''You just want tae f -- -- up on drugs so that everyone'll think how deep and f ---- complex you are. It's pathetic, and f -- -- boring.'' Renton allows as how this explanation is as good as any. It certainly applies to the denizens of those Hollywood parties, not otherwise noted for their lives of deep feeling and despair. ''Their self-doubts tell them they're getting rich because of their cheekbones,'' a screenwriter told the New York Times. ''You become consumed with doubts about your authenticity and look for authenticity in areas that are, unfortunately, cliches, such as the heroin-using artist.''

This, then, becomes heroin's ultimate appeal: it's the fashionable way to be authentic, the latest ticket to being alienated and with-it at the same time. Irvine Welsh, the author of Trainspotting, denies nasty rumors that he himself was never a problem user. In Pulp Fiction John Travolta, a self-assured character miles away from angst-ridden twenty-year-olds, uses heroin. And so did that 21-year-old model on the August cover of Newsweek, beckoning to us with her fine and innocent features. Being driven into the arms of a dangerous drug by the conviction that life is a pointless bore never looked quite so good. If Kurt Cobain had it to do over again, no doubt he'd be careful to become addicted to something else.