The Italian wine invasion of America is in full swing. And if the surge continues, this vinous army might well become the most potent Italian force since Ceasar's Legions. In the past six years Italian wine shipments to the U.S. have rocketed from 9.5 million gallons a year to over 39 million, double the yearly total of all wine brought in from France, Germany, Portugal and Spain. Naturally, not all of this is classic wine: Over 60 percent of it is fizzy lambrusco and more than half the remainder is simple soave, valpolicella and bardolina.

Still, that leaves enough wine of promise to tempt even a wine bibber whose allegiance is solidly linked to France or California -- or was until the price of their wines began to attain heights previously reached only by astronauts.

The rush to find less costly wine has sent some local shops on Italian buying sprees, a few to the extent that they now display upward of 90 different bottlings. Further, Washington can now boast of an importer who brings in only the better wines of Italy.

Clearly, something's going on we should know more about.

Unfortunately, there are way too many Italian wines (over 200 are legally defined by the government) to get a good handle on them by random sampling. It's necessary to concentrate on a more manageable grouping.

I settled on wines made from the nebbiolo grape, aristocrats of Italian reds that flourishes in a belt 50 miles either side of the Turin-Milan autostrada.

Well over two dozen varieties are produced in this area of Piedmont and northern Lombardy, not all of which make their way out of Italy in any quantity. Nevertheless Washington stores yielded a dozen nebbiolo-based wines in nearly 100 different bottlings.

In three sessions, a hardy group tasted 41 of these and found both pleasant surprises and lamentable disappointments.

The biggest surprise was that almost without exception the most popular wines were the least known. Often they were the least expensive. A good bottle for under $5 was common; some of the best cost only a bit more.

The bad news was the general mediocrity or unavailability of Nebbiolo's big three: Barolo, barbaresco and gattinara.

Results of the initial tasting, which focused on the first two, can be found in the accompanying box.

Best knowb of these and hardest to love is the barolo. The problem, as all tasters quickly learn, is that barolos need 10 to 15 years of bottle age, even with their longer time in wooden barrels (at least two years by law). Without the age they are harsh, mouth-puckering wines that not even Pollyanna could love.

According to DOC (Denominazione di Origine Controllata ) requirements, bottles labeled Riserva must have four years of aging, two in wood and two in glass; Riserva Speciales age five years before being offered for sale.

This longer wood aging turns barolos (and other similarly aged nebbiolo wines) a browner color and imparts a woodier, more mature taste to the flavor, which is made more lively and sharp by the higher acid level. It is this latter characteristic that makes them ideal companions for rich food.

Unfortunately, I could find no older, quality barolos in Washington. Rumor has it that there are some in New York, San Francisco and Los Angeles. Vintages to get if you're in those neighborhoods are 1964, 1961 and 1958.

Perhaps one day soon local shelves will display not only mature barolos but bottles from those top-notch producers currently comspicuous by their absence.

In the meantime, the 1971s would be my choice for cellaring, particularly Molino, Fontanafredda and Terre del Barolo. The 1970 Fontanafredda also displays good prospects.Just remember it will be three to five years before they're ready.

Of those I tried independently of the group -- 1967 Pio Cesare, 1967 Rinaldi, 1969 and 1970 Giri, 1964 and 1970 Villadoria, 1971 Kiola and 1971 and 1974 Marchesi di Barolo (the '74 is a single vineyard Riserva) -- only the '70 Giri, the two Marchesis and the '67 Pio Cesare impressed me as above average, and I've encountered some dubious bottles of the Pio.

As to that old wheeze that urges you to open your barolo hours, even days, ahead of serving, recent experiments on both sides of the Atlantic indicate that a mere hour's decanting prior to drinking is usually best. I tried all the wines in our tasting 24 and 48 hours after opening and found only a couple that may have improved. All the rest declined.

Barbaresco, like its neighbor barolo, is named for a tiny village southeast of Turin and is 100 percent nebbiolo. Unlike barolo it is softer and rounder and takes somewhat less aging to reach its peak -- legal requirements call for a minimum of two years for the regular bottling, three for the Riserva and four for the Riserva Speciale.

Sadly, there are very few of any of them in Washington.

In addition to those in the tasting, I tried 1964 Gaja and 1965 Bersano, both unimpressive, 1971 Marchesi di Barolo (pleasant and rather forward) and 1967 Pio Cesare. The last time I had the latter it was delicious. Apparently others agreed, for it seems to have disappeared.

The youthful Vietti, good as it is, clearly needs more aging; the Fontanafredda is much closer to drinkability, maybe as close as a year or two. CAPTION: Illustration, no caption; Chart, Barolo and Barbaresco