On the streets of Rome or Hamburg, they are surrounded by fans and followed into restaurants for autographs. They are the Yankee snow twins, conquerors of Europe's steepest mountains and greatest ski heroes. Anywhere there are snow-capped mountains in Europe or Japan, the Mahre brothers are big time.

Rarely has the spotlight fallen on such reluctant stars.

"Neither one of us is real big on being celebrities or heroes," said Phil Mahre, 25, a 1980 Olympic silver medalist and two-time World Cup champion who has teamed with his fraternal twin, Steve, in the last two years to set the international skiing world on its collective ear. "It's pleasant for a change to go home to the U.S. where nobody knows me."

The Mahre brothers are the kind of sports heroes for which the United States used to be famous. They are modest, square-jawed and private. They are fierce competitors, gracious winners and good losers. And both have refused to cash in on either the glitter or the gold that is available at the highest level of amateur skiing.

"When the skiing season is over, we'd just as soon be home pounding nails or working on our cars," said Phil last week while he and his brother were in Washington raising money for the U.S. ski team. The two, dressed in sport coats and ties that might have come from Robert Hall, certainly did not look like international ski stars.

If the Mahre brothers have not let success turn their heads, the folks who run this country's Olympic ski program have been more than a little impressed. Except for brief peaks of greatness, U.S. skiers in the last half century have been so far behind in international ski competition that Saint Bernard dogs have been needed to locate them. The Mahre brothers, and some head-first women racers, have changed all that.

Last winter, the U.S. Alpine ski team enjoyed its best record ever. For the second year in a row, Phil Mahre won the overall World Cup title. He also won the slalom title, beating Sweden's Ingemar Stenmark, who had won it eight years in a row, and also separated Stenmark from his title in the giant slalom, which the Swede had won four consecutive years.

Brother Steve, meanwhile, finished in third place overall and won a gold medal for giant slalom in the world championships in Schladming, Austria. He was the first U.S. male to win a gold medal in an Olympic or world championship in 51 years.

No U.S. woman did as well as the Mahre brothers this year, but the women's team won the Nations Cup competition, finishing 60 points ahead of runner-up West Germany.

That success does not mean that the United States has any permanent claim to the world's mountains, warn U.S. ski officials. Once the Mahre brothers ski away, it may be a long wait for another U.S. male star to come along.

"We do not have a national development effort worthy of being called a program," wrote Tom Corcoran, chairman of the Alpine Advisory Committee, which has overview responsibilities for the U.S. Alpine team, in the November issue of Ski Racing. "We are totally dependent . . . on the emergence of athletes as talented as the Mahres, and they are exceedingly few and far between."

The Mahres were speeding down Washington mountains at the age of 6. Their father was the manager of a ski resort at White Pass, a town with a permanent population of about 30. When the Mahre brothers weren't skiing, it was usually because there wasn't any snow.

At 16, Phil was named to the U.S. national team. The next year, Steve was picked. One year later, both were in Europe, competing on the international tour and establishing reputations as skiers who were technically flawed but as fast as runaway sleds.

"Sometimes, you concentrate too much on being technically perfect and forget to go fast," said Steve, who has broken as many bones as his brother in his short career, but lags behind in the number of plates and pins that keep his bones together.

The Mahres have been intensely competitive for as long as they can remember, but say they rarely squabble and have had only one actual fight.

"We were about 11 or 12, up in our room," remembered Steve, whose short, brown hair is thinning on top in exactly the same places as his brother's. "I hit Phil real bad and made him cry. That made me cry."

Some of their international competition complains, jokingly and otherwise, that it is not fair to have brothers competing in the same events. One will finish the course, then give his brother tips on how to plan his run.

"I get to the bottom and radio my comments so he can beat me, not Stenmark," said Phil. "We're two against the world, but we're also against each other."