The chance to see Phil Kay (Gilded Balloon) in front of an audience who know how much they can expect from him is one of the great joys of the Festival. After he devoted the whole of his opening night in 1995 to a miraculous one-off wedding ceremony, expectations are running high as the hyperactive Scot takes the stage for the first of this year's eight shows. As Kay's train-of-thought speeds off recklessly down overgrown branch-lines, the passengers hanging on for dear life behind him can feel comedy's most basic mechanisms at work: "It's like ... What's it like? Something that's the same."

The problem with spontaneity is that it's hard to get it to work consistently. The problem with building the audience into your act is that the chances are they aren't as funny as you - that's why your relationship with them is as it is. But Kay's mix of stock jokes - "I took some MC squared: it's great, it's just like E" - and extravagant flights of conceptual fancy carries him through. His routine about the roar of flashbulbs at Olympic medal ceremonies - everyone taking that shard of time and space home with them and thus crinkling the fabric of the universe - is worthy of the great Vegas club act Bert Einstein.

Those comedians grinding their teeth at missing out on this year's Perrier award should comfort themselves with the knowledge that West Country minstrel Bill Bailey's scandalous omission from last year's shortlist has turned out to be the best thing that could possibly have happened to him. This year's show at the Assembly Rooms is a great improvement on its predecessor. The intervening 12 months have given Bailey time not only to come up with a great stage-set - a marvellously gruesome 3-D rendering of a classic King Crimson album cover - but also to broaden his base and up his energy level without losing his roots in back-from-the-pub philosophy. Some of his new material - the Chaucer routine, the boy-band songwriting exercise ("Boy is sad / Girl not there") - is worthy of Willie Rushton at his best.

It's good to see last year's Perrier victor, Jenny Eclair, still tearing up the Pleasance Cabaret bar, even if there is the odd moment in her new show Wig Out Teeth In ("All new stuff! Trust me, I'm an award winner") when you can almost see her manager holding a gun to her head and forcing her north of the border. Whether playing professional Philistine ("That Rubens, he painted some fat ugly birds didn't he?") or morbid aphorist ("A personality is the last refuge of a woman in decline") Eclair continues to keep the line between her act and her actual personality cunningly blurred. John Redwood may one day wish to use her relationship with her

daughter as an illustration of the true meaning of motherhood: "I can't wait for her to become a teenager," Eclair gloats. "She'll be like fresh bait on the end of my hook."

A yawning chasm of cultural difference threatens to open up in front of ebullient Californian James Stephens III (Assembly). Not because he is the only non-caucasian comic to appear solo at any of the Festival's three main venues, but because some of the big names in his vocal repertoire (Stephens is a kind of hyperactive, soul-based Joe Longthorne) are not exactly of the household variety on this side of the Atlantic. All the more impressive then to elicit a standing ovation with impressions of Michael McDonald - the not-quite-legendary ex-lead singer of the Doobie Brothers. One question remains though. Why do so many black American comedians seem to think that being gay or of oriental extraction are funny in themselves?

Stephens's fellow American Rich Hall (Gilded Balloon) provides the answer to this and many other questions with his amazing world map of humour. It links all races via currents of ridicule - "The Poles make fun of Chad: not the country, just the one guy" - and shows why all jokes finish their working lives in Germany: "They're trapped there, they can't get out." If there was a prize for best individual gag at this year's Festival, deserving Perrier nominee Hall's "Do you know how many Vietnam veterans it takes to change a light bulb?" would be a hot favourite. It would be wrong to destroy this joke by printing its punchline in a national newspaper, but an SAE will secure a response.

Away from the legions of male stand-ups that colonise so much of the rest of the Edinburgh comedy high-ground, something very interesting is happening. It's almost as if the ghosts of the Alternative era have at last been exorcised. Now the nation's politicians are embracing the apolitical stance that has been de rigueur among laughter- getters for the past 10 years or so, perhaps there is an opportunity for comedians to get their teeth into something slightly meatier than Star Trek.

Admittedly, this is currently a vague feeling rather than a concrete phenomemon - the only tangible evidence for it at the moment is Al Murray's great pub-landlord character and Harry Hill's superb trade union / jam analogy - but this year's bumper crop of adversarial double-acts seems to back it up. Ivor Dembina and Omid Djalili's barnstorming The Arab & the Jew (Pleasance), Ancona & Francis's polished and subtle Miss-Conceptions (Gilded Balloon II) and Bert Tyler Moore and Will Smith's fluffy Sorted For Teas & Bics (Pleasance II) all celebrate difference (in race, gender and sexual orientation respectively) rather than similarity.

And all the while Lee and Herring (Pleasance), that most evenly matched of double-acts, are educating a new generation of comedy aficionados to an unparalleled level of sophistication. Topical as ever, Stewart and Richard supply avuncular advice to those among their impressionable teenage fanbase whose exam grades may not be all they had hoped for: "Just lower the expectations you have for the rest of your life."