Open Monday through Saturday, 11:30 a.m. to 11:30 p.m. MC, V. Reservations. Prices: Average lunch (three courses, tax and tip, without wine) $10; average dinner $15. Light supper about $5.

It takes a certain critical mass for a string of restaurants to coalesce into a restaurant neighborhood; that point has now been reached in the vicinity of 3rd Street and Massachusetts Avenue NE. People stroll from the Man in the Green Hat to the new American Cafe, maybe as far as the Gandy Dancer, looking at menus and sneaking glances at what people are eating, sizing up the lines for outdoor tables, asking people how they liked their meals and choosing a place for dinner.

More and more, the choice is La Brasserie. The line stretches, and hungry people discuss what they ate during the last visit, often greeting and chatting with friends who have already cadged tables.

What, you may understandably ask, is La Brasserie? It is that pretty little cafe that started as La Ruche, was renamed Maxime, and has undergone a change of management and menu under this new name. The tile tables set inches from each other are the same.The bakery counter filled with glistening fruit tarts remains intact. The upstairs room is still lighted by large windows overlooking the avenue. And the walnut cake is as good as ever. What has changed is the menu and the cooking, and while on successive visits it seemed still in flux, the signs were good.

What still needs to change is the service. It is pleasant, convivial and spirited, but unreliable. One course may come slowly, another quickly. The waitress may stand around and discuss your wine or disappear with no thought to bringing your check. If you intend to hang around, La Brasserie is a good place to do it. You can appreciate the staff's good nature more than its efficiency.

La Brasserie has gradually revamped the old La Ruche menu, but still needs to pare away some items that don't show it to advantage. That makes it an insiders' restaurant, where it is important to know how to get a fine meal. If you look around, you will spot the insiders by the bowls with pastry domes sitting in front of them. They start with la bourride, a creamy seafood bisque presented under a top hat of flaky, buttery pastry that crumbles into the soup as you eat it. It is a spectacular soup, nearly a meal at $2.25. I would not want to slight the onion soup, a broth of depth, but the bourride is a rare find. On a hot day you might want to start with a pate; it is countrified and pungent with liver, quite good one day, bland and gristly another day. A salmon mousse with green peppercorns also lacked sufficient seasoning, though it was a commendable creamy fluff. Begin, perhaps, with a salade Raymond, an imaginative contract of crunchy walnuts and smooth blue cheese with endive and watercress, well tossed with vinaigrette and served on a large cold plate.

Every day brings fresh main courses handwritten on the menu, and each list includes fish and veal, both of which the restaurant does well. Truite a la Hussarde was stuffed with buttery, highly seasoned bread crumbs and topped with an even more buttery sauce. It was very rich and all the better for it. Soft shell crabs were not only cooked beautifully, they were savory with lemon and garlic, a more tangy version of that dish than I have had anywhere in town. Among fish courses, only the quenelles were a disappointment, lacking an airy, custardy texture and sufficient seasoning, and oddly sauced with cheese and a watery cream sauce. Veal has been uniformly successful, whether a thick, tomato-sauced chop or simple, golden-crusted veal francaise.

The everyday menu also lists scallops with leeks, crab with curry, two steaks and lamb chops in pastry, all of the main dishes ranging from $7 for the quenelles to $9, except for the soft shells at $11.75. At lunch the main courses are considerably less; veal francaise, for instance, was $5 at last check.

If that were all the choices, La Brasserie would be just another competent, mid-priced French restaurant. But it also serves light dishes - puff pastry filled with chicken or seafood, quiches and double-crusted vegetable pies, as well as hefty salads (and a few sandwiches at lunch). Because the pastry is skillfully made at La Brasserie, these are good choices, as long as they are not overcooked in the reheating. One day's vegetable quiche was tired, overworked, though it had obviously showed early promise.

These ragged edges need attention, as do the vegetables that accompany main courses. One day the summer squash with tomato and onion was a compliment to the veal. Another day the mishmash of peas, mushrooms, cauliflower and carrot, all disintegrating, seemed an accumulation of the week's leftovers. Ratatouille was delightful one day, but the hard, chewy rice that shared its plate was not.

Significantly, pastries occupy a major portion of the menu, in addition to providing the main decorative accent to the downstairs dining room. And, in the La Ruche tradition, they are just short of excellent. What pulls them up short is the puff pastry on the tarts and the napoleon - heavy and dry. The other components, the custards and fruits, are worthy of better. And the cakes - crunchy walnut cake and spongy chocolate roll fat with whipped cream - have no such flaws. But the most extraordinary (and, at $2, most expensive) dessert is creme brulee. Creme brulee is an inspired combination of smooth, double-rich custard under a crust of burnt sugar, its caramel flavor and crunch contrasting wonderfully with the soft texture and dairy delicacy. It is a dessert rarely attempted by restaurants and usually insulted by the few attempts. At La Brasserie it is superb.

Thus, Washington adds another to its list of moderately priced, moderately ambitious French restaurants where the food is good and the setting unpretentious. But this one is bracketed by a remarkable beginning in its bourride and a remarkable ending in its creme brulee.