Expect fire and the swallowing of sharp objects when the first Street Performance World Championship begins, writes Peter Crawley

In general, whether they're charging about in a hurry or simply out for a stroll, people hate to be stopped. The modern defences of mobile phones, iPods, or the straight-ahead stares that ward off intrusion have rendered the average city-dweller almost impervious to unwanted advances. All of this means that the feat of arresting someone's attention has become something more than a challenge. It has become an art form.

The Space Cowboy is such an artist. The Cowboy, sometimes known as Chayne Hultgren, is an Australian juggler, unicyclist and sword-swallower. (Although, having also temporarily ingested fluorescent lightbulbs, his swallowing rarely discriminates.) If such antics tilt towards the repulsive, you forgive him for his charisma. I've seen crowds cluster around his riveting performance - building from juggling manoeuvres through increasingly funny audience interaction and steaming towards his signature crescendo - and I've never seen anyone walk away before it's over.

If you haven't seen someone riding a 10ft-high unicycle while juggling a knife, a flaming torch and a sickle - all while blindfolded - such feats are set to shock and delight anyone in the vicinity of Dublin's Merrion Square this bank holiday weekend as part of the first Street Performance World Championship.

Unicycle or no, all street theatre performers essentially undertake similar balancing acts performed without a safety net, their displays juggling charm, talent and spectator engagement, while ultimately depending on the generosity of an audience.

For the past year or so, Conor McCarthy and Mark Duckenfield, the new festival's organisers, have learned a lot about such risky business.

It began one May evening in Temple Bar when the two men in their mid-twenties found themselves engrossed by an acrobatic performance that had drawn, they say, close to 600 spectators. They watched for three hours as the show repeated. "And each time the bucket, or the hat, was getting filled again and again," Duckenfield recalls.

Here, they realised, was an art form that Irish people were willing to reward - although they had no obligation to do so - "and yet there's no infrastructure for it." Pressed to identify a venue for street performers, most Dubliners might point you in the direction of Grafton Street. But late-night limbo dancing and doddery living statues are of little concern to the family-friendly Street Performance World Championship.

"A lot of the Grafton Street stuff would be 20 minutes long," says McCarthy. "These buskers" - the 10 international acts they have attracted to Merrion Square - "are at the top of their game. They have a set 40-minute show and that's their show. They've thought of the idea, they've moulded and shaped it into something that is just constant 'hit' throughout the whole 40 minutes. It starts with getting the crowd in - it builds, builds, builds - and then there's a big finale."

With the usual Grafton Street performers, people just stroll by, agrees Duckenfield. "You stay for a couple of minutes and then you leave. With these shows, nobody wants to leave."

Indeed, so alluring is world-class street performance that McCarthy and Duckenfield abandoned their day-jobs to devote themselves to organising a festival in its honour, modelled on similar events in Christchurch, New Zealand and Shizuoka, Japan. Why McCarthy, a former software engineer, and Duckenfield, who used to sell a paper-shredding service, should give up the excitement of their former professions is not for us to guess, but if there is something of an endless summer in their attitude, the seriousness of their undertaking - and their ambition - is not in question.

"Our aim in this is to create the biggest street performance festival in the world," says Duckenfield.

"We want to bring to Ireland the equivalent of the Notting Hill Festival and the Edinburgh Fringe festival. We want to have a huge festival in the city centre, so in years to come it won't just be in Merrion Square, but around the city in different locations. In order to do that the performers have to come here and have an amazing time. They don't arrive to a commercial structure where there's branding everywhere. It's a carnival provided by Dublin City Council."

"No over-priced paninis," nods McCarthy. "None of that kind of thing."

Supported by Dublin City Council and Fáilte Ireland, the festival's lack of branding sets it apart - it is, after all, a free event - but this disinclination towards commercialism also means that the festival organisers' company, Emergent Events, is unlikely to be able to pay its directors for their time. McCarthy and Duckenfield are hoping that in years to come, when funding becomes more reliable, this will change.

In the meantime they're in a less secure position than even their acts: when the show is over the organisers won't have a hat to pass around.

This is all rather faithful to the time-honoured tradition of street performance, or busking (the terms have slightly different connotations but are used interchangeably). From Commedia dell'Arte to Punch and Judy, organ-grinders to Bob Dylan, street performance has been as much a vocation as an enterprise.

Talk to any of the festival's participants and you will generally hear variations on the same story: their development as performers, their gradual understanding of how to attract and hold a crowd, their commitment to what they do, and their love of freedom from regularity. Grant Goldie, for instance, was originally a bar manager from Norfolk who is now a Belfast-based street performer operating under the name That Man.

"The first time I ever went out on the street to do my act, I couldn't even get anybody to stop," Goldie remembers. This was, to say the least, a hindrance to his busking career, one he overcame by constantly refining his act. Deciding that he was no good with jokes or punchlines, his last major modification was to go silent - something that, oddly, has made it easier for him to communicate with a crowd. This is the sort of lesson you can only learn from the unforgiving attention spans of the passer-by.

"The street is the toughest place to do something," Goldie agrees. "You have a captive audience in a theatre where you can just get on and do your stuff. The street is definitely a hard place to do things. But it's hugely gratifying, as well, when you do get people to stop. You pull them away from what they ordinarily do during their day. My show is about transporting people into slightly different worlds, and bringing something into people's lives that they're not expecting to see. The smile that will then come across people's faces is hugely gratifying."

Rebecca Higby, one half of Boston's Yo-Yo People (her husband John is the other half) might agree, having developed a show that incorporates hula hoops, unicycles and, of course, yo-yo tricks. It's not all fun and games though.

"You can feel like a rock star one day," says Rebecca. "Everybody loves you and everything works. The next day you're doing the exact same show and nobody will even stop. Folded arms and sour faces. At the beginning of the day you just don't know what kind of show you're going to have. It's constant theorising: maybe it's the weather, or the kids aren't out of school yet, or maybe it's a Monday. All these theories why a show works or doesn't work. We haven't figured it out yet."

Considerably less genteel than the theatre, and more prone to heckling than a comedy club, the street is an unpredictable venue. But when an audience does gather, circling naturally around one engaging performer, it provides an unmatched feeling of unity and participation.

The American serial death-defier Greg Frisbee, whose resumé of achievements includes being abducted by aliens and holding a degree in Media Communications, has learned to respect that audience's judgment. "Oh totally," he says. "I mean you learn very quickly what's working and what's not. If you're doing something that you think is really cool, but the people don't find it cool, they're going to walk away."

Together, Frisbee and his audience have discovered that someone juggling knives and flaming torches is not necessarily cool, but someone juggling knives while actually being on fire is always cool. How Frisbee achieves this, or how Dan Menendez can perform a classical piano recital by bouncing juggling balls on the keys, or how the Space Cowboy stays upright on his 10ft unicycle, is the easy part.

Asked what the biggest obstacle to their inaugural outdoor festival might be, McCarthy and Duckenfield think for a moment, but neither volunteers the impediment that every street performer fears the most: the weather. If the organisers seem sanguine, it may be because they draw from the busker's deep well of optimism. Whatever the weather, the Street Performance World Championship awaits us, the product of their blue-sky thinking.

• The Street Performance World Championship takes place in Merrion Square on Sat, Aug 5 and Sun, Aug 6. Details available at www.spwc.ie