As the world's number one producer of bubbly, the Champagne region would be proud, you might think, to see its methode champenoise tag used by other sparkling wines made by the same process. Not so. The term was outlawed in 1994 in the EU for all but champagne itself. Now these wines may use only nebulous terms such as methode traditionelle or methode classique, with diminished information value.

If the aim was to keep rival fizz producers at bay, the champenois may have succeeded. In California, where vast amounts of surplus champagne cash have been sunk into grandiose sparkling wine facilities by Champagne's grandes marques, their insistence that these sparkling wines are emphatically not champagne helps to maintain the price gap between champagne brands and the more affordable local fizz.

To protect themselves from being cannibalised, ie letting their champagnes be swallowed up by their own California fizz, the champenois have even ruled against using their own names on their California bubbly. Early birds such as Moet et Chandon, however, with Domaine Chandon, and Mumm, with Mumm Cuvee Napa, have managed to have their cake and eat it by clinging on to their names, with no apparent detriment to their champagnes.

Not that the champagne method in itself is the be all and end all. If it were, all methode champenoise wines would, by definition, be superior. But as is obvious from cava, for instance, Spain's champagne-method fizz made from Catalonia's rustic macabeo, parellada and xarello grapes, there is considerably more to top quality sparkling wine than a second fermentation in the bottle and a minimum period of ageing on the lees. For starters, there's quality grapes.

Before California fizz was even a twinkle in Moet et Chandon's eye, Schramsberg was the first local producer to realise that to make world-class wine, you need world-class grapes. Jack and Jamie Davies pioneered the quality fizz revolution in 1965 by resurrecting Jacob Schram's 19th-century subterranean caves and planting the champagne grapes, pinot noir and chardonnay. They continue to delight in cocking a snook at the champenois by calling their sparkling wine "champagne".

When the French champagne houses followed Schramsberg into the Napa Valley, picking the grapes unripe was their first big mistake. Grapes picked at the same potential alcohol levels as those in Champagne were simply too green, resulting in lean and mean wines, to which overcompensating sweetness was added back at the dosage stage. After a decade of trial and error, the major players have made adjustments, picking the grapes later, opening vineyard canopies to sunlight and obtaining lower yields for riper flavours.

The big boys of the Napa Valley now obtain an increasing amount of their resources from growers in cooler Carneros and Sonoma vineyards. Roederer, Piper Heidsieck and Deutz set themselves up in ultra-cool, Pacific-influenced districts, respectively the Anderson Valley and Russian River Valley north of Napa, and Arroyo Grande on the Central Coast. The result is grapes with more delicate skins, more flavour and a better balance of natural acidity.

Refinements in the cellar, such as gentle pressing and blending from different vineyard sources, allow wine makers to fine-tune to a far greater degree than was possible a decade ago. Tricks of the methode champenoise, such as blending in reserve wines from previous years, selection of yeasts and lengthy ageing on the lees, contribute to the creamy-textured cushion of bubbles and toasty flavours of ageing in bottle which typify quality fizz.

Ironically, just as production methods were beginning to improve, the champagne houses that went bright-eyed into California suddenly found the ground shifting from under their feet. To their dismay, the American public discovered chardonnay and the health benefits of drinking red wine - at the expense of sparkling wine. Fizz, in a just-say-no era of diet and drink-drive awareness, was considered by many to be too frivolous to count as wine at all. This was the trigger for a change of policy and a decision to woo consumers outside the US. Seagram-owned Mumm was the first to make an impression on this side of the Atlantic, with Mumm Cuvee Napa, enthusiastically marketed by Seagram-owned Oddbins. Where Mumm Cuvee Napa boldly went, others have now followed. Among the more successful are Roederer, with its crisp Quartet; Pommery, with the rich, full-bodied Scharffenberger; Taittinger, with its stylish Domaine Carneros; and Spanish- owned Freixenet, with Gloria Ferrer. Most recently, there is Piper Heidsieck's superbly crafted Sonoma Pacific range - relying, unusually, on substantial stocks of reserve wines aged in oak casks.

While the champagne houses have added sparkle to California's fizz industry, local producers such as Schramsberg, Iron Horse and Jordan have not been left behind. Each of these houses now produces sparkling wines as good as, and in some cases better than, their champenois rivals. With warmer vineyard sources, the Schramsberg and Jordan house style is in the richer, no-holds-barred vein veering towards the Bollinger-esque. The Russian River Valley's Iron Horse in contrast consistently produces the most elegantly austere styles

California crackers

Mumm Cuvee Napa Rose, pounds 8.99, (pounds 7.71 at seven for six), Oddbins. Pale salmon pink, crisp, pinot noir-based strawberry-cup style fizz with youthful, fresh fruitiness: one of the best value California sparklers.

Sonoma Pacific Brut, pounds 9.99, Fuller's. The latest recruit to California's export drive, this seductively aromatic, honeycomb flecked Sonoma fizz is a stylish, creamy-textured and delicately toasty blend of mainly pinot noir grapes.

Gloria Ferrer Brut, pounds 8.95, Adnams (01502-727222), pounds 9.99, Majestic, Wine Cellar. Fine, yeasty, champagne-like aromas and a well-balanced, creamy- textured cushion of bubbles, from Spanish Freixenet.

Domaine Carneros Brut, pounds 12.29, Terry Platt, Gwynedd, Wales (014925-92971). This pale sparkling wine from Taittinger's French replica chateau is very elegant, with delicate brioche aromas and a balance between lightly toasted richness and tangy acidity.

1991 Schramsberg Brut Rose, pounds 11.95, Lay & Wheeler, Colchester (01206-764446). This is an outstanding, mainly pinot noir-based, salmon-pink rose with a deliciously creamy mousse and complex, bottle-developed flavours.