Open for lunch Monday through Saturday 11:30 a.m. to 2:30 p.m. and for dinner 5 to 10 p.m. Reservations suggested. MC, V. Prices: Lunches with soup, salad, main dish and rice $5.50 to $7.50; at dinner $4.50 to $12. Average dinner with wine or beer, tax and tip $15 or less.

The hamburger is getting crowded out by ever more exotic competitors, none more unexpected than sushi. Who would have thought that Americans -- unfairly credited with inventing the well-done steak -- would have taken raw fish to their hearts, or their mouths?

We now have shopping centers with not only Chinese restaurants and bagel bakeries but also sushi bars. New among these is Tsukiji, hidden behind Bob's Big Boy of Rockville Pike but still discovered by a band of faithfuls.

At first glance Tsukiji is just another luncheonette converted into a sushi bar, and after a couple of meals there it is apparent that the fish is not fresher than average, nor are the cooked dishes better than ordinary. The small room is rather standard, one wall lined with orange leatherette booths and the other with a sushi bar, the whole made slightly oriental by Japanese hangings, slightly festive by blue tablecloths and utterly Americanized by hanging colored glass lamps.

The first outstanding characteristic is the prices. Sushi here is $2 an order -- that's $1 per piece -- and even rolled sushi (maki) are $2. An order of sashimi (four pieces of raw tuna) is only $3. That makes it at least as cheap to order sushi a la carte as in an assortment. Most main dishes are about $7.50 to $8.50, and that includes miso soup and salad. But even so, at Tsukiji I would stick to the sushi.

The second factor that makes Tsukiji special is the personnel. The owner and the sushi chef both communicate well, explaining dishes that nearly defy description, and they also are friendly and gracious. It makes a big difference when you don't know the subtleties of three kinds of clams or the possible combinations of fish and seasonings that might be made into seaweed-wrapped rolls. The sushi chef is also a first-class craftsman: his sashimi platters are lovely still-lifes with clam shells and seaweeds artfully arranged, and his sushi plates are charmingly garnished with fanned-out cucumbers dabbed with salmon caviar. And in his combination rolls he goes further than most, adding scallions, radish sprouts and sesame seeds to the grilled salmon skin roll, sesame seeds to the crab and avocado in the California roll, and decorating those rice-coated rolls with tiny orange specks of flying fish roe.

There are certainly Japanese restaurants in town where the fish is firmer, more moist and more fresh; where the tuna is less fibrous; where the negimaki -- thinly sliced beef rolled around scallions -- is more juicy and meaty. The dumplings called gyoza, are nicely browned and delicate little noodle envelopes, but their filling is bland. And the tempura is reasonably light and crisp, but not noteworthy. Swordfish grilled with either salty (shioyaki) or sweet-salty (teriyaki) marinades is well seasoned, perfectly fresh fish but a bit chewy. But some dishes, such as tuna with sticky, gummy and bland yamaimo, or a plate of strongly fishy little fried fish called shishamo, require some time before a taste can be acquired for them.

The appetizer list includes bean curd several ways, fish or mushrooms with grated radish, yakitori and a delicious little dish of cold boiled spinach with sesame seeds and bonito flakes. Main dishes include several teriyakis and a couple of pork dishes along with tempuras and noodle dishes. The point of Tsukiji is the sushi bar where sushi and sashimi are good values.