Despite a growing reputation as the best horror film director working today, Guillermo del Toro is loathe to characterise most of his movies as true 'horror'. Donald Clarke talks to the Mexican film-maker about a career path that began with Super-8 when he was a kid and culminates with his latest extravaganza, Hellboy

With Cronenberg sitting upmarket, Craven increasingly dull and Romero out of work, a case could be made for Guillermo del Toro as the best director of horror films working today. The 39-year-old Mexican, who first made an impact with the 1993 vampire drama Cronos, has managed to stay true to his singular sensibility - fantastic, extravagant, darkly humorous - while building a reputation for delivering solid (if never spectacular) returns at the box office.

Only 1997's Mimic, in which giant insects tried to eat Mira Sorvino, has failed to win over audiences and critics. Since then del Toro has triumphed with the spooky Spanish chiller The Devil's Backbone and impressed with his unnecessarily imaginative sequel to the Wesley Snipes vehicle Blade. Now comes Hellboy, a hugely enjoyable adaptation of Mike Mignola's comic book about a refugee from Hades who ends up working for the FBI's paranormal division.

Annoyingly, del Toro isn't sure he is a horror director at all. "And that's all I really wanted to be," he laughs. "Mimic is really the closest I have got to making a pure horror film. I always mix other things in. Cronos had so much melodrama. Hellboy has comedy and adventure. Blade II is in many ways an action movie, and Devil's Backbone is a very human drama. The closest I have come to a horror action movie is Mimic."

An enormously friendly and personable character, del Toro resembles a cleaner, not quite so enormous Michael Moore. Born in Guadalajara in 1964, Guillermo was hooked on horror before he could walk and made his first Super-8 movie at the tender age of eight. His juvenilia have become a great source of debate in horror nerd circles. Are there hidden gems in his Mom's attic?

"Oh they were very strange and very bad," he says. "I unearthed some of the best of the Super-8 period recently and I was going to transfer them onto video for the 10-year-anniversary DVD of Cronos, but they were just too stinky. We used some snippets. But even they look pretty crappy."

Tourist guides to Mexico always make a great deal of that country's singular relationship with death. It is said that festivals such as Día de los Muertos (Day of the Dead) evidence a more comfortable relationship with oblivion than that enjoyed by Europeans. Is this all baloney?

"No. Carlos Fuentes always said that Mexicans don't come to death, they come back to death. Yes, as you say, the Day of the Dead is a touristic way of looking at this. It is the Mardi Gras approach. But, yes, there is a race to death in the Mexican mindset."

So that and his youthful addiction to horror films made him the artist he is? "Yes. When you are a kid there are very few things that show you a radically different attitude to the world. Horror films introduce you to the weird. Everything else kids are shown is just about goodness, and that is so castrating. Monster movies are just so liberating. I found them such a great escape."

Del Toro first broke into commercial cinema when he set up a company specialising in horror make-up and effects. Eventually, after a great deal of hectoring and bargaining, he put together enough financing to make Cronos, a remarkable film about an elderly antique dealer who discovers a device that grants immortal life (with a price). Co-star Ron Perlman, later to play Hellboy, still enjoys joshing the director about the pressures that came with such a small budget.

"He loves to tell one story where I had just finished a take and yelled: 'Cut. Check the gate.' And Ron said: 'Can't we do one more?' And I said that it was perfect and the crew all cheered. But Ron insisted. So eventually I had to take him aside and tell him that we just had no more film. None at all. The reason why Hellboy and The Devil's Backbone are my favourite films is because they are the ones where I was most in charge. Cronos was constant battle."

The Mexican state institutions which helped finance the film were faintly appalled with what del Toro delivered, and he had a real fight getting Cronos released. He turned up at Cannes with 10 posters, a roll of Scotch Tape - "That was our entire publicity campaign" - and no great expectations. So nonchalant was he that when it was announced that the film had won the Critics' Week Grand Prize, he was out having dinner with his wife.

Moguls didn't begin beating down his door immediately. "I owed half a million dollars on Cronos and nobody seemed very interested in me." Eventually he was signed to direct Mimic for Dimension Pictures. It was not a happy experience. In his recent book Down and Dirty Pictures, Peter Biskind tells how Dimension boss Bob Weinstein (brother of Harvey) attempted to sack del Toro in the middle of production, but was forced to relent when Sorvino threatened to follow the director out the door.

"I think that the story in the book was told from the point of view of a single source," he says. "I don't think that story is quite accurate from either side. I don't see the world in such a simple way: these are good guys these are bad guys. What I learned on Mimic was if you think you are making a different film to the one the studio thinks it's making, then just don't do it. But going into any more detail on this will just encourage gossip."

I suppose any director must have to assume a commanding posture on set, but del Toro seems so sweet and eager to please that I can easily imagine him being eaten alive by the likes of Weinstein. Did he consider returning to Spanish-language pictures for good?

"The Hollywood experience has always been a by-product of necessity," he says. "I never thought that I would fit in there. After Mimic I really thought that I might not go back. I was happy doing The Devil's Backbone. What happened was Hellboy. I heard that they wanted to do it." He adopts the tone of a Mexican Pacino. "Just when I thought I was out, they pull me right back in! Ha ha!"

A self-confessed comics geek, del Toro had been a great fan of Mike Mignola's boxy demon with the filed-down horns ever since he first appeared in a 1993 Dark Horse comic. The release of Hellboy marks the culmination of six years of negotiation on the director's part.

"Part of the problem was that the character and the origin and the story were very different to the normal Hollywood product," he says. "I jokingly say that this is a very personal movie disguised as a summer blockbuster. It was actually quite hard to pitch: it's a film about a demon who is conjured up by the Nazis in 1944 and who goes on to become a paranormal investigator. 'Who does it star?' they asked. 'Ron Perlman.' How much does it cost? Well, it's not cheap. Right there you have six years of conversation."

Del Toro pulls out his notebook to demonstrate how intricate his designs for the production were. He is a wonderful artist and his lengthy notes are interspersed with beautiful little drawings of characters and situations. It comes as no surprise to learn, considering how clear his thinking is, that he was adamant that nobody would dissuade him from casting his favourite lead actor. But, terrific as the bulky Perlman is, he is nowhere near a marquee name.

"I grew up watching films starring Robert Mitchum and Lee Marvin. And I thought: now that is a leading man. But now Hollywood seems to be obsessed with leading boys. I cherish ageing over youth. Ron represents a quintessential humanity in the way a Russian realist statue represents the working man. You know people value youth and beauty way too much. And those things have a very low exchange rate when you come to die."

Hellboy did pretty well at the US box office, and del Toro finds himself regarded as a safe pair of hands. Hisnext picture (Pan's Labrynth) will, like The Devil's Backbone, tell a macabre tale against the backdrop of the Spanish Civil War. ("I just find that conflict one that is as close as wars get to a battle between good and evil.") Then he will direct Hellboy 2. But what happened to his long-held ambition to create an adaptation of H.P. Lovecraft's wonderfully dark story At the Mountains of Madness? That would surely give del Toro an opportunity to produce the classic horror film he has, by his own reckoning, so far failed to deliver.

"I am in the fortunate situation that DreamWorks are big fans of Hellboy. Spielberg loves it. So they are keen on doing Mountains of Madness. I keep saying that will be my Titanic, which, of course, could be taken two ways. But I really hope that will define the horror genre for me. I just hope it doesn't become my Waterloo." Our mouths water.