A relative unknown on this side of the Atlantic, the American artist Alex Katz will reach a wider public with a new exhibition this week

Whatever you think of his taste in art you can't help but be impressed by the slickness of the Saatchi machine. No sooner has Sensation closed at the Royal Academy than a barrage of pre-publicity arrives to announce "the first exhibition in this country of one of America's most important post-war painters". They refer to Alex Katz, a name which may not ring too many bells on this side of the Atlantic, but who has long had a following elsewhere and more recently has become the subject of Charles Saatchi's extraordinary passion for wholesale acquisition.

Actually that isn't quite fair. For all I know Saatchi could have been secreting Katz's pictures away for a quarter century, but somehow I doubt it. Either way he now has 26 of them, spanning roughly 25 years, and from Thursday they go on show at his gallery in St John's Wood.

Unlike much of the work that makes up Saatchi's much publicised collection Katz's pictures seem clear enough: large, flat images of people or landscapes, not unlike something from a billboard or advertising hoarding stylised and stylish in a post pop-art sort of way. One can see why an ad-man like Saatchi likes them.

Katz's champions (who number such heavyweight American critics as Simon Schama and Hilton Kramer) claim that there's another level and talk about the poetry in the pictures. I'm not sure about this, but once again we should be grateful to Saatchi for bringing them to London and for giving us the chance to decide for ourselves whether Katz is America's best kept secret or yet another example of his patron's famous hype.

The Saatchi Gallery, 98a Boundary Road, NW8 (0171-624 8299) 15 January-12 April