In terms of crowds, competition, money and world attention, the World Alpine ski championships that open here today will be the biggest thing to hit this town since Adolf Hitler opened the Winter Olympics here 42 years ago.

In 1936, Hitler stood at the ski-jump finishing area while some 50,000 people looked on from a stadium that still stands today.

But now, the choicest land next to the finishing line for the championships this week is occupied by the U.S. Army's Sheridan barracks and recreation area.

Though the world has changed greatly since 1936, Garmisch has not, though there is now a McDonald's here. It remains a picture-book Bavarian ski town - clean, colorful, expensive and nestled at the foot of spectacularly beautiful mountains, including the 9,2000-foot high Zugspitze, Germany's highest.

It is not a "jet-set" sort of place. It has been a Mecca for skiers for too long, ever since a rail line was hooked up from Munich opening up the town to tourists in 1889. Since then, the town has grown gradually and it handles seasonal crowds with comparative ease and without giving up too much of the area's quiet conservatism.

Indeed, though there are some 60 mile of ski slopes in the area, the mountainsides seem to contain almost as many aged but tough German lady and gentlemen hikers - devoted to a lifetime of walking, "frische luft" (fresh air) and a small glass of clear schnaps at the end of their walk - as do skiers.

There have been World Cup ski races here several times in recent years. They were one or two-day affairs that are part of a three-month traveling ski circuit that spans a dozen European sites each year.

But this is the first time here for the world championships, a five-day event that draws far larger crowds and is swelling Garmisch's normal population of some 30,000 people to more than double.

A brass band from the West German army's Mountaineer Division will herald today's opening with a flourish of trumpets in the stadium, welcoming some 300 entrants from 35 countries. Though the band may wind up playing the Austrian, Swedish and Swiss national anthems mostly for the winners, they have memorized all 35 anthems with typical German efficiency.

The world championships are three-one-shot winner-take-all races.There is a single downhill run for men tomorrow and the women on Tuesday, and two runs each in the men and women's slalom and giant slalom events on Thursday, Saturday and Feb. 5, with the best combined slalom times winning. A single spill means its all over for any skier.

The no-second-chance aspect adds great drama, especially for a ski-crazy Europe. But the skiers themselves tend to regard these once-every-four-year championships as less of a true professional test than the results of the three-month-long World Cup circuit where a skier may race 30 times a year.

Nevertherless, the World Champoinships - held midway between Olympic Games - are big. "Nobody wants to wait four years to see the big stars," says U.S. team doctor Robert Leach. "It's like World Series time in New York or basketball playoff time in Boston."

"It focuses world attention on the sport for a short but important period," adds Hank Tauber, the director of the U.S. team. "But its probably second to the Olympics Games themselves."

The championships mean big money, too. Advertising banners are springing up around the courses, though Garmisch has controlled the hucksterism somewhat better than Austria did earlier this month. There, so many companies hung up banners beyond the area where they had to pay for it but within the viewing area of television cameras that German and Swiss TV - in a great act of hypocricy in the view of many observers - declined to televise the World Cup races.

Exposure here, but more importantly victory, can mean financial life or death for the major ski manufacturers who sell some nine million pairs of skis a year around the world. It is especially crucial for countries like Austria, where skiing is truly a major industry and where their stars are national heros.The Germans have sunk almost $9 million into hosting this event, perhaps more than the 1936 Winter Olypmics cost.

The big event will be the men's downhill - a test of skill and courage that will send racers hurtling down a steep and snaking two-mile mountain-side run, with drops in places of 28 degrees, in some two minutes time at a winning average speed of probably above 60 miles per hour and with peak speeds of 75 miles per hour.

Nearly 20 years ago, the great Austrian downhiller Karl Schranz won a major downhill race here with an average speed of 47 mph, a testimonial not only to how skiers have improved but, perhaps more importantly, to the enormous role that technology - waves, clothing and ski design - now plays in this competition.

In Austria last week, 12 World Cup skiers finished within one second of each other, an dfour within 9 one-hundredths of a second.

As championship courses go, Garmisch is not rated as the fastest or most dangerous, though a Canadian racer was killed here in 1959 and the younger brother of Austria's reigning top downhiller, Franz Klammer, is partially paralyzed after a spill on this same course last year.

From the relative safety of a cable car climbing to the mile-high starting point, the downhill course looks suicidal to the eye of the nonskier. Off to the sides of some curves, nets are being hoisted in place to catch anybody who may go slashing off into space - perhaps a skier from Iran or Morocco, Ireland or Turkey - countries that don't figure anywhere in world ski standings, but who show up nevertheless.

The drama here will be provided by several of the big names like Klammer, whose blistering downhill runs have been compared to a run away stagecoach, and who may end his spectacular, quasi-amateur World Cup career soon and turn professional.

Can Sweden's 21-year-old Ingemar Stenmark, who is heading for his third World Cup slalom victory but who has never won an Olympic or world championship, and the world title to his extraordinary career?

Will Austria's 24-year-old downhill snow queen Annemarie Moser hold onto her title and reputation after a 20-month voluntary layoff and will Lise-Marie Morerod, hold off a stiff challenge from several top women skiers, especially Liechtenstein's Hanni Wenzel?

For the steadily improving Americans, the ebig question and drama is whether Olypmic bronze medalist in the downhill, Cindy Nelson, can score on the same course here where she broke her ankle a year ago. And, whether 20-year'old Phil Mahre, now fifth in the World Cup standings, can break through closer to the top of the world's best in the slalom events, or perhaps capture a combined point total medal if he also competes in the downhill.

As in the past, however, there are apt to be some surprises from a number of younger, less well-known skiers - including a trio of American women: Abbi Fisher, Christian Cooper and Becky Dorsey.