Open daily from 11:30 a.m. to 2 a.m., weekends until 3 a.m. AE, MC, V. Reservations. Prices: pastas $5.25 to $6, main courses $6.50 to $8.50.

Washington, unlike Baltimore, Philadelphia, New York and Boston, has never had a Little Italy. For a while I thought there was a possibility in Bethesda, where a cluster of Italian restaurants opened within a couple of years, but that trend has reversed. Now, however, the most secretive Little Italy ever prrceived may be in the making.

It started with Da Vinci, an expensive Italian restaurant that at first impressed the eye and only in recent months impressed the mouth. After a quiet beginning, Da Vinci has now gathered followers for some truly excellent food: pastas of delicacy, Thursday night pheasant with spinach gnocchi. Across the street opened Marshall's which hides behind its burgers-and-booze bar a tiny dining room serving Italian food. And even more unexpected, a few blocks away, a restaurant with an unlikely location-upstairs from La Ruche-and an unlikely high prices. So this week we have evaluated Italian restaurants by any other name. Forget your images of red-checked tablecloths and hanging chianti bottles. This Italian restaurant looks like Georgetown East (which it is).The front room is a bar, with disco and folk music on the jukebox, which somebody kicks every time it gets stuck. Hamburgers and draft beer are the specialite de la maison. The rear dining room, however, might have been dropped off by mistake and stayeds because it was comfortable. A scant dozen tables are candlelit and often centered with sprays of dried flowers in pottery vases. Darkly painted ceiling and floor, brown linen napkins against the white floors, louvered wooden wall panels and church pews of deeply waxeds golden wood cast a dim, warm setting. With such a small room, there is only one waitress at a time, but each is singularly vibrant and eager to serve well. The waitresses seem intent on making you enjoy yourself as much as they are enjoying themselves.

It is a lean menu at Marshall's , and appropriately so. The highlights are the pastas-cannelloni, straw and hay, and linguine with zucchini and broccoli or white clam sauce, ranging from $5.25 to $5.95 or $3 for a half-portion. All are home-made, the linguine's long wavy ropes cooked al dente and sauced subtly with garlic and olive oil or with cream and a complexity of sausage, peas, mushrooms, prosciutto and cheese. Even when the broccoli and zucchini are portioned skimpily on occasion, the linguine preparations are excellent. Cannelloni is less professional, its noodles thicker than necessary and the combination heavy and robust rather than fresh and delicate. Still, it is good.

Among appetizers are some simple and appealing scampi in garlic butter and the sleeper of the menu, a batter-fried vegetable and cheese plate, at $3.25 enough for a small meal. Mushrooms, green peppers, cheese even tomatoes are fried in a very light, crisp batter and served with a dip sharpened by mustard. Fine nibbling food.

Main courses center on veal, with a couple of chicken and seafood dishes to balance. The kitchen uses good quality veal and cooks it skillfully, though sometimes it has been overpounded. Someitimes, too, there is a heavy hand with herbs, so the saltimbocca's sage overwhelms even its prosciutto. Still, you can't go far wrong with the scaloppine or with the veal chop stuffed with prosciutto and fontina cheese and lightly breaded. Boneless chicken breasts are also expertly cooked, though there is a tendency to sprinkle too many garnishes on them; nobody needs artichoke hearts, capers and peas all at once on a chicken breast. As for seafoods, there are shrimp, sole and calamari; a calamari sample would have been delicious if the herbs had been more restrained. Marshall's has a special affinitry for broccoli, serving broccoli soup, linguine with broccoli and broccoli as a vegetable accompaniment. No wonder. They cook it beautifully. They also make several desserts on the premises-cheesecake and lime pie most frequently. They,however, are more commendable in the thought than the product; the textures are flawed, and the cheesecake tastes more salty tha sweet.

Marshall's wine list is small, but its house wines are Italian imports at respectable prices, and the markup on bottled wines is modest, compared to the outrages being presented at other Italian restaurants downtown. For $8 or less there are seven Italian wines that Spencer's, for instance, sells for more than $12.

Marshall's serves a non-Italian Sunday brunch that has become a weekly routine in its neighborhood. With champagne, it runs about $8 a person. For dinner you are likely to spend $15 to $20 a person. You are likely to spend the evening, too.