With noses pressed against the display window, a trio of teen-age Italian girls stood in front of the shoe store discussing their forthcoming purchases: identical pairs of fringed, bead-studded leather moccasins, advertised as made in the U.S.A. by Oglala Sioux Indians.

An influx of imported shoes -- moccasins, sneaker and running shoes from the United States and low-cost sandals and casual wear from Third-World and developing countries -- is causing some head-scratching among shoe producers here already faced with a sharp decline in the domestic market.

But it is only one aspect of a severe crisis in the Italian shoe industry that is leading manufacturers here to rethink the future. Last year overall shoe production here declined by 12.4 percent, with leather shoes -- the bulk of Italian production -- dropping by over 18 percent.

Exports, a mainstay of the industry, suffered an even greater drop: 21 percent for leather shoes and 16 percent for the footwear industry as a whole.

Sales to the United States, Italy's second-largest shoe client after West Germany, dropped by more than half, from 97 million pairs in 1979 to 47 million pairs in 1980. This has caused grave difficulties for many of Italy's 8,000-odd shoe manufacturers.

"Foreign orders have almost completely dried up," says Paolino Grossi of Minos Shoes in the Tuscan city of Pistoria. Last year his small, export-oriented firm with 14 employes was forced to suspend production for a month, and the outlook for this year is even worse, Grossi says.

"This is not the first time that the Italian shoe industry has been in trouble," says Titti Cappiello, an economist working on a study of the sector. The present crisis is far worse than a 1973-1975 slowdown "and will not only force the industry to retrench but compel it to make some significant changes."

Shoe production, a traditional Italian handicraft that in some areas of the country goes back to the Middle Ages, has been a major foreign exchange earner here since the 1960s. In 1978 Italy, a country of 56 million people, produced almost 6 percent of the world's shoes to become third-largest manufacturer after the Soviet Union and China.

In the peak year of 1979, shoe firms located mostly in Tuscany, the Veneto region, Emilia-Romagna and the central Italian area known as the Marche exported a total of 375 million pairs of shoes.

At an average of 8,348 lire, then worth about $10, these sales earned the country about $3.7 billion, almost a third of what the country spends for oil imports yearly. But over the past two decades, much of the Italian industry's success was based on its ability to provide quality products at very low, competitive costs. The situation, however, no longer exists. Shoe manufacturing is a highly labor-intensive industry and, with Italian labor costs spiraling, manufacturers here are gradually being forced out of the market.

The current crisis in part reflects some very specific circumstances. In 1979, for example, almost a third of the nearly 100 million pairs of shoes exported to the United States were "candy shoes," women's high-heeled wooden clogs wit colorful plastic strips across the front of the foot that have since gone out of style.

And overall changes in fashion have also left many Italian manufacturers out in the cold. For example, western youth today prefers running shoes and other casual wear to the classic shoes that make Italian shoemakers famous. "Look at the kids going by on the street and you'll see most are wearing sneakers," said one manufacturer whose $40 leather loafers, once a sure bet, are no longer selling.

But in general Italian production costs have become too high to compete withe the low-priced shoes produced not only by European countries like Greece and Spain but increasingly by Brazil, India, South Korea, Hong Kong and China.

By the end of 1980, for example, labor costs in much of the Italian shoe industry (though sweatshop wages still exist in some parts of the country) had risen to about $8.50 an hour compared with only $6.50 in the United States. Costs in the large Italian leather tanning industry also have scored.And while market conditions this year have improved, in recent years the price of imported goat, sheep and cattle hides also have escalated, in some cases by as much as 280 percent.

Officials at ANCI, the Italian shoe manufacturer's association, believe one problem is the nonreciprocal system of generalized preferences that the Common Market currently gives to developing countries, allowing shoe imports to increase in recent years by as much as 80 percent to 90 percent.

Another is the import restrictions -- for the most part quotas -- imposed in the last few years by countries like Argentina, Canada and Japan, eager to protect their own shoe manufacturers.

But the main problem will be that of adjusting to today's world. Since they no longer can compete in the production of low-cost casual wear, some Italian shoe producers believe the only answer is to concentrate on the high-priced quality product.

"We've got the craftsmanship, the know-how and the professional expertise," said one manufacturer. "What we're missing is better marketing techniques and a dose of luck that will being the classical back in."