Best In Show director/co-writer/actor Christopher Guest has mined a rich vein of comedy out of the wannabe-famous. Best known for his involvement with cult rock 'n' roll mockumentary This Is Spinal Tap, he has also jabbed at showbiz wannabes in the Big Picture, and sent up amateur performers who dreamed of stardom, in Waiting for Guffman.

Best In Show, which this time targets those who desire fame for their show dogs, is sure to please fans of Guest's particular brand of gentle mocking and slightly zany comedy. Others may feel that it lacks the potency to sustain a feature-length comedy, although it is not without its hilarious moments.

The structure mirrors that of the fly-on-the-wall documentary genre, threading interviews with events as they happen. Taking the maxim that "Every dog owner ends up like their dog" - or "is it every dog ends up like their owner?" - no matter, we are introduced to a range of dog owners on the eve of the Mayflower Kennel Club Dog Show. There is a gay couple and their ribboned Shih Tzu's (those dogs that look like long-haired slippers); a dead-pan Southern fishing-store owner (played by Guest himself) and his long-faced bloodhound; a yuppie couple and their sleek, but neurotic Weimaraner, and so on.

The actors appear to improvise, which creates an air of authenticity, but also means that some of the humour can come across a little flat and obvious. Also, as character-based comedy goes the doggie people have a certain affectionate quirkiness, but their scope for comedy is limited. By the time the dog show itself starts half way into the film, it is down to the colourful invention of a foot-in-mouth television commentator (Fred Willard), blithley adding a series of cringeworthy comments ("'Shih Tzu'... sounds like..."), to save the whole film from sagging completely. This is light and enjoyable, but it's not another "Spinal Tap".