On the Via Monte Napoleone, women wear miniskirts under mini furs, usually with colored tights and low-heeled shoes, as they window-shop the posh boutiques. At La Scala, black taffeta miniskirts are popular, and one woman wears a red lame' version with gold hose and ballet slippers. In the subway, a young woman sports a pink flannel, inexpensive copy of Giorgio Armani's cuffed short skirt which pokes out from under her black leather blouson.

At the Royal Palace, as part of a large exhibition of Fascist art of the 1930s called "Anni Trenta," there is a small fashion exhibit. Most of the clothes are derivative of the Paris designers admired at the time by Italian women. An extraordinary collection of hats, jewelry, buttons and sportswear documents the period.

The international fashion crowd here this week cannot escape the street fashions of today--decidedly above their American counterparts at the hemline--or the historical exhibits. But the main concern is what will happen next.

That they are about to find out at the Milan Fairgrounds this week, when 34 Italian designers show their collections for next fall. About 1,200 buyers and 440 members of the press will view eight shows daily.

Last season the message was clearly short skirts. At two showings yesterday, hemlines were shown both above and below the knee--above the knee for those few who haven't tried it yet and below the knee for those who need to be lured into something new.

More will be known today and tomorrow when such heavy hitters as Gianni Versace, Gianfranco Ferre, the Missonis, Krizia and Fendi, send their models down the runway to be photographed and applauded--and perhaps noted by buyers for later purchase when stores place their orders.

Generally, clothes are expected to shape up with broad shoulders and rounded sleeves to make them more roomy. Wide belts will wrap the natural waist or drop over the hips. Designers have found new ways to make leather and fur lighter weight, though Versace has reversed the trend by mixing metal with both leather and knit. Strong, clean shapes are expected for daytime, plush velvets and elaborate embroideries for evening.

Giorgio Armani, star player in this fashion competition for the last four years, will show for buyers but not for the press. In a letter to the press last month he said he would hold a press showing "at a more appropriate time." Armani's plan to show his collection a month after other designers was reminiscent of what Paris designers Balenciaga and Givenchy did in their heyday to keep others from copying their couture creations.

Armani thinks of himself as an "industrial designer." He designs 30 collections including his own licencees, men's clothes and accessories. He sells his successful cheaper line, which includes jeans, cotton knit tops and suede polo shirts, at his shop called "Emporio Armani." By next September, he says, there will be 50 more such shops in Italy.

With the addition of a perfume to be introduced later this month in Paris, Armani expects to jump from a $170-million company to a volume of $250 million. The perfume introduction happens to coincide with the date Armani would like reporters to start writing about his new clothes.

But even without a press showing, Armani is a strong influence here with women, who wear variations of his short culottes and his hip-belted styles, and with other designers who borrow his way of doing shows. Last season he scaled back his presentation by showing clothes pinned on the walls of his Palazzo Durini showroom rather than on runway models.

Luciano Soprani followed suit yesterday by displaying his Helyett collection on mannequins. At Helyett and Gianfranco Ferre's less expensive collection called "Oaks," hemlines were both above and below the knee.

Carla Fendi watched supermodel Alva Chin try on an above-the-knee dress made shorter when the model latched a clear vinyl belt over her hip. "This isn't a mini," Fendi insisted, but didn't define what this mid-thigh length could be called. "Mini, morta!" she exclaimed emphatically.

Still, short skirts everywhere in the city indicate that Washington women will be baring their knees this season.