There is nothing like a Damien

Film director, restaurateur, pop musician and - oh yes - the country's most famous living artist, Damien Hirst clearly relishes his celebrity. But on the eve of his first exhibition for nearly five years, surely he must be feeling just a bit apprehensive?

Damien Hirst is surrounded by underpants. The Hieronymous Bosch of Leeds, the psycho wunderkind of the British avant-garde, is standing in London's Joop gallery swamped by fundamental garments. Wherever you look, there are unmentionables in all shapes and textures: outsize pants, pants crusted with sugar, pants hardened with wax, pants covered in industrial cleaning fluid, pants adorning the thighs of a skip-load of inflatable women, pants made of chocolate, pants festooned with rose petals, pants on the hindquarters of a furious-looking bulldog...

Damien Hirst is surrounded by underpants. The Hieronymous Bosch of Leeds, the psycho wunderkind of the British avant-garde, is standing in London's Joop gallery swamped by fundamental garments. Wherever you look, there are unmentionables in all shapes and textures: outsize pants, pants crusted with sugar, pants hardened with wax, pants covered in industrial cleaning fluid, pants adorning the thighs of a skip-load of inflatable women, pants made of chocolate, pants festooned with rose petals, pants on the hindquarters of a furious-looking bulldog...

We're at a design exhibition mounted by Joe Boxer, the American underwear corporation which disdains advertising in favour of chic marketing events like this one. It has invited the cream of design students from the Royal College of Art to come up with bright ideas related to clothing and eccentricity: and the results are to be judged by Hirst himself.

The great man is dressed down today in navy jacket, jeans, T-shirt, and has the blank-eyed, sticky-up-haired demeanour of one who has only recently risen from the arms of Morpheus. He puffs on a ciggie as he scrutinises Lauren Bonner's Momento, in which the clichés of zodiac signs are given a dusting; he nods approvingly at the depiction of Aries as a ram's horn impaling a canvas bag - a very Hirst-esque image of male genitalia - and poses for photographs with Hannah Ball's amusing entry, My Boyfriend's Favourite Bra - a brassiere that features twin TV sets showing a football match in progress.

Hirst wanders through the gallery with a proprietorial air, inspecting this exhibit, murmuring encouragement to that palpitating student. For a champion épateur of the art establishment, he seems at home as the smiling, celebrated public man, the kind of guy who donates work to charity auctions and is guest artist at the Louvre. This is called stardom. He clearly relishes it.

He's judging this event as a favour to Nick Graham, Joe Boxer's ebullient Canadian owner, who is a friend. They met via Danny Moynihan, Graham's cousin, and for whose first novel, Helter Skelter, Hirst designed the dust jacket (a carving knife slithering across a bloodied floor). "It's all pure nepotism," says Hirst sadly. He and Graham have, since I expect you're wondering, occasionally discussed doing a range of Damien Hirst Y-fronts (with transparent pouch of cow guts?) but it's never really taken off. "I was thinking of doing some glass ones," said Hirst. "But of course you could never sit down in them." He considered. "What would be really good would be a pair of underpants with a thing on the side for holding your pint. Because I'm always getting my trousers down in bars."

Indeed. One thing everybody knows about Damien, apart from his fondness for bisecting cattle with a chainsaw, is his obsession with body parts, especially his own penis. Late-night drinkers at London's Groucho Club have startled their more shockable friends by describing Damien's party trick involving his foreskin and a 50p bit. A fan of the two-man Penis Puppets show that's been wowing the Edinburgh fringe ("they do the Hamburger, the Drumstick, the Winged Serpent, the Crispy Fried Peking Duck..."), he fell foul of the law recently when trying to emulate them. "I was doing the Chicken Bone in a bar in Dublin, and this woman from Boston got upset and now she's suing me for $50,000." What's she suing for? Hirst smiled. "Toxic shock."

Hirst's normal discourse is a hectic muttering, in which half the words get lost, but a hundred more arrive to take their place. He is a chronic mickey-taker and anecdotalist, but is surprisingly strait-laced when talking about art - even about painting, of whose formal oil-and-brush decencies he is, of course, the great subverter. A certain gravity is in order now, for he is about to put himself on display, and in a more meaningful sense than the Dublin pub episode. On 23 September, his first exhibition in four and a half years will be launched at the Gagosian Gallery in SoHo, New York.

The big surprise, he admits, is that there's nothing pickled in this one. It's free of formaldehyde. On the other hand, "I've got two gynaecologists' offices under water, with tropical fish swimming around in them". No really, he means it. They're life-size offices, seven foot by seven, called Love Lost and Lost Love, the crucial difference between them being that "one's got English river fish, the other's African river fish". Surprisingly, the fish in this new exhibit aren't doing anything (mating, breeding, being electrocuted) apart from swimming around.

Hirst has no time or temperament for worrying about critics. (He admires Brian Sewell, who once admired Hirst's work but came to loathe it. "When Brian was having his heart-bypass op," said Hirst, "he promised he'd let me have the bits of his insides, in formaldehyde. I said, Great, I'll make a piece called The Best Thing That Ever Came Out of Brian Sewell. But I'm still waiting.") He admits, however, to feeling apprehensive about likely reactions to two installations. "One's called Death is Irrelevant, and is a skeleton leaning back looking like Jesus Christ only with ping-pong balls for eyes. And the other's two autopsy tables with bodies on them, not real bodies, of course; they're covered with blankets and there's bits of chicken sticking out. I've called it Adam and Eve Banished from the Garden. I think the religious stuff might cause a problem. I mean, this Giuliani character's a bit weird, isn't he?"

You look in Hirst's green eyes for a trace of irony, a smirk of sarcasm, but find none. To him, the outgoing mayor of New York's objections are weird, whereas his impulse to find images of the grotesque, the visceral, the repulsive and the unsettling could not be more normal.

He has discoursed proudly about his childhood photo-library of burn victims, his cherished colour-pix manual of venereal diseases, his morbid fascination with decay and guts, that sits so oddly alongside the antiseptic "colour spot" pictures, the medicine-cabinet installations, the interest in restaurants. Just as there's a Mrs Tiggywinkle side to Hirst, obsessively compartmentalising and labelling the animate world, there's an element of Jeffrey Dahmer about his goggle-eyed inspection of human ordure. Brought up a Catholic by his mother Mary Brennan, he rejected the religion but liked the iconography. "I liked all the gory pictures in the Bible, the guy on the Cross, the crown of thorns. Kids that age, they love a bit of gore. That's how they sell you religion - to satisfy your carnal desires."

Since 1988, Hirst's biggest fan and personal Medici has been Charles Saatchi, the virtual inventor, or convener, of modern BritArt, and behind the "Sensation" exhibition that scandalised New York. Earlier this year, Saatchi paid £1m for Hymn, a 20ft bronze model of a child's toy. It's likely that anything Hirst made could be parlayed into a further million. Does he ever feel... spoilt?

"Oh yeah, a lot of people say, 'You could sign a piece of dog dirt and people would call it art'. But why the hell would you do that? What I think about my stuff is, if I throw it out in the street and it's not there in the morning, it must be good."

Did he reject a lot? "You throw away a lot of ideas. I wanted to have a pig with vibrators stuck all over it, so you could call it Pork-U-Pine. I thought it was great for about eight minutes and then I went, 'No, you can't do that, it's rubbish'." So he was aware of a bullshit detector in his head? "There's a visual language that exists," said Hirst. "It's got to be enjoyable, it's got to brighten the room up, it's got to be fun and entertaining." This Rebecca-From-Sunnybrook-Farm approach to art, while endearing, seems a little hard to take square with Hirst's dual-autopsy aesthetic.

He's now 34, probably the most famous artist in the country, his work commanding the third-highest prices (after Lucien Freud and David Hockney). He lives on a farm (and 30 acres of land) in Devon with his Californian wife Maia and their sons, Connor and Cassius. He has, in his brief career, made a short film ( Hanging Around), directed a pop video (Blur's "In the Country"), had a hand in opening two London restaurants (Quo Vadis and Pharmacy) and another hand in creating Fat Les, the conceptual supergroup co-starring Keith Allen and Alex James, whose football anthems "Vindaloo" and "Jerusalem" entered the consciousness of the British public like a rat entering a drainpipe. For a man who got an E in A-level art, Hirst is doing very well.

Was he concerned about the opening of the New York exhibition? Did he ever feel apprehensive? Did he ever doubt his own worth? Hirst looked baffled, as if I'd suggested he might not possess testicles. "No, I'm not worried about it at all," he said shortly. "I haven't done anything for four years because I was worried about it. I didn't have anything to say. I haven't done it until now, until I'm sure about it."

So his quality control thing has been working overtime? "Yeah. "If in doubt - leave it out. OK?" And, pausing only for some spectacular face-pulling at a passing snapper, he and the Canadian underpants king are off to the pub for a chinwag about the lady with the TV-football bra.