There has been a healthy air of anticipation around Joanne Tatham and Tom O'Sullivan's new Tramway show. There were the occasional rumours of ''something really big'' going on in what is, after all, the largest gallery space in the country. Then an unusually elegant private-view card, emblazoned with the mysterious letters HK, arrived, along with the information that the pair, who graduated from Glasgow School of Art's master of fine arts course in the mid-nineties, have been working with the controversial issue of drugs.

Tatham and O'Sullivan are consistently intriguing artists. Their sculptural works have included references to such diverse subjects as rave

culture, amateur craft, eighteenth-century painting, surrealism, sixties minimalism, studio ceramics, and teen movies.

Their installation, The Glamour, shown at Transmission Gallery last year and then at the Berlin Biennale, involved barbed wire, pink fluorescent lighting, mirrors, and literally tons of rubble. It's as though they feel quite free to rummage round the skip of art history for anything they can recycle and put to good use. They're not just ragpickers, though, but astute construction workers, putting their pieces together with intelligence

and a keen satirical eye for some of the more wearisome cliches of installation art.

By forcing these contradictory elements to sit down together in one room, they are constantly begging the questions of whether art is any more than just style, and why it has developed its own language, so divorced from our everyday conversation. Ultimately, they are asking if art and the rest of life can rub along, or if they're destined for a series of misunderstandings, secret admiration, and mutual mistrust.

Although all of this had aroused my curiosity, none of it had actually prepared me for the jaw-dropping experience that is HK, an artwork that at first sight is so simple and so audacious it actually made me gasp out loud. The installation starts in the lobby of Tramway, with reading a

wall of moving, complex stories,

transcribed from interviews with

people affected by heroin use, including a user, a drug worker, and a bereaved parent.

Entering Tramway 2 you see HK for what it really is: an empty and enormous slogan. The words HEROIN KILLS writ out in three-dimensional black letters, each some six metres high. They tower above you, looking like something from Stonehenge or The Flintstones, something dropped out of the sky like the opening titles of Monty Python's Flying Circus. The words are huge, empty, fatalistic, and indisputably true. HK is physically overwhelming, yet so woefully inadequate a response to the stories relayed outside, that it's almost laughable.

Tatham and O'Sullivan know what they're up to. The slogan recalls the government's spectacularly unsuccessful Aids campaign from the 1980s, featuring creaking tombstones and equally creaking logic. And the embarrassing plotline from school soap Grange Hill, where cute and cheerful Zammo became a desperate drug-addled junkie, and the cast made a hit record admonishing schoolchildren across the country to Just Say No.

There's art in here, too. The 1980s sloganeering of Jenny Holzer and Barbara Kruger, the cool conceptualism of Lawrence Weiner. The letters are so large that you can walk through them and under them, find yourself nestling under the crossbar of the H, tempted to dive through the centre of the O. It's like seeing one of those immense metal sculptures by Richard Serra, which are so big that when you walk around them you are secretly terrified they're going to fall on you.

BUT HK is also kind of thrilling, in a punk, 1970s New York kind of way. You think of Lou Reed's miserable album Berlin, of the writer and addict Alexander Trocchi. You find yourself seduced by the seedy glamour of it all, aware Tatham and O'Sullivan are pushing at the edge, knowingly opening themselves to accusation of triviality and exploitation over such a serious issue.

Last week new research showed that 3.8% of Glaswegians between 15 and 54 are misusing hard drugs such as heroin or methadone. There are 2.6million drug-related crimes every year. If it's a commonplace cliche in art that truth is beauty, what do we do when the facts are as ugly, as unconsoling as this?

HK isn't going to answer that, but it's an admirably provocative and somewhat bloody-minded contribution to the discussion.

HK is at Tramway until January 20 next year.