Open for lunch Monday through Friday noon to 2:30 p.m., for dinner Monday through Friday 5:30 p.m. to 10 p.m., Saturday 5 p.m. to 10 p.m. Closed Sunday. AE, CB, DC, MC, V. Reservations. Prices: Soup with sushi, sashimi or tempura at lunch $6.50 to $14. At dinner sushi or sashimi a la carte $6.50 to about $22 a person. Full dinners $16 to $28 a person and up. Full dinners with sake or beer, tax and tip can run $45 a person.

A few steps up from 20th Street, the Great American Fast Food has been transformed into the Great Japanese Fast Food; burgers have given way to sushi. Take sushi, a sushi bar highly respected in New York and Tokyo, has opened a Washington branch.

Sushi has much in common with American fast food. You can sit at a counter, eat quickly and run. Surroundings are clean-lined -- in this case, blond wood dividers and tables set with small sauce dishes and chopsticks in paper envelopes but no tablecloths, all on a grass-green carpet. The menu is short, just assorted presentations of raw fish, a couple of soups and tempura in case you like something hot. And the "kitchen" consists largely of cutting boards, a futuristic-looking rice pot and a few toaster ovens.

But this is fast food that takes a chef who has been trained for perhaps a dozen years, and can cost as much as the most expensive French or Italian restaurants in town. Lubricated only with beer and sake, dinner one night (without dessert) cost us $45 a person.

Before you write off Takesushi for budgetary considerations, note that you could also eat a simple everyday sashimi or tempura lunch for under $15 a person. A tray of sushi from the menu runs $6.50 to $14, depending on its size and quality; an ordinary sashimi selection is $10 to $12, and tempura is $8 at lunch, $16 as a full dinner (with soup, two side dishes and dessert). Lunch entrees are accompanied by miso or clear soup; a la carte they are $1.50. The escalating prices we encountered at dinner are signaled by the word "omakase," which the menu defines as "our chef's daily offering from a specially selected superior grade of fish."

We first heard the word as the waitresses in kimonos, quite gracious and fairly if not totally acquainted with English, carried glorious-looking dishes to a group of Japanese men at the next table. First, small fish curled and skewered to decorate a salad of julienned fish (imported from Japan, the waitress told us). Then, a platter of raw fish looking like sea jewels, some of which we had never seen before. Omakase. That was what we wanted.

What we got was a beautiful platter with smoked salmon slices curled into a full-blown rose, tuna--both dark and the pale, fatty and delectable belly section; firm and fresh, unctuous and irresistible yellowtail; a ruffled clam shell filled with slightly crunchy slices of some sea mystery. There were strips of sweet and firm clam, oddly crackly herring roe strips, several curly and bubbly-looking seaweeds. And that glamorously decorated fish salad, topped with scallion and ginger and tasting wonderful. Pearly white fish had been sliced thin enough to see the plate through it, and arranged in petals along one side.

It was a grand platter, and five of us took our time enjoying it, until we found that it cost about $75 and that we were still very hungry, even after soup and tiny dishes of vinegared fried fish that accompanied the sashimi. So two of us ordered sushi, a nice assortment with tuna, clam, eel, egg, salmon, some white fish, crisp roe, sea urchin and salmon roe. Excellent, but at $43 it worked out to $2 a bite. Three had tempura, which reiterated what I had discovered at a previous lunch, that Takesushi's is the best tempura in town, the shrimp crisp and juicy and retaining their flavor under their pale gold lace of a batter. The carrot, sweet potato, broccoli, onion and white potato had just a veil of crust and were cooked through, but just. The doily underneath attested to the restrained greasiness of the tempura.

Even the miso soup was especially good, with a full, breezy, salty flavor and tiny cubes of soft bean curd. The clear soups tasted more watery, though they had been nicely garnished with omelet shreds or with egg drops.

Fine points set this apart from ordinary sushi bars. The fish-topped rice cakes have a particularly precise look, and the platters of sashimi are clearly artistic, with fish rolled up like flowers or sprinkled with a few grains of coral roe. While no sushi fish in Washington is going to be fresh by Tokyo standards, these fish taste carefully handled, and the shrimp has a fine flavor that is absent from routine cooked shrimp. The variety of sea creatures is wider than Washington is used to seeing, and surprises such as those lovely silvery curled-up fish show up intermittently. If you watch the sushi chefs at work, you will see new and different shells filled with unexpected seafoods. It pays to be bold and ask questions, or you will leave feeling as if you missed some rare treats.

The problem is communicating what you want and in the waitresses' communicating what you are getting. But the situation has been constantly improving. On my first visit I couldn't manage to get menus. On my second visit it took about eight requests to get tea. By the third, the service was prompt, the handleless mugs of green tea were frequently refilled and the menus had covers. Everything was more organized, though the waitress still nodded to everything we asked without actually giving us any clear answers.

Portions at Takesushi have a Japanese delicacy that is not reflected in the bill: Takesushi's prices are authentically Japanese, which means high to breathtaking. Thus, while the quality is also high, you can get betterrvalue elsewhere. The most blatant example is chirashi, a lacquered box filled with a bed of vinegared sushi rice and topped with, in this case, eel or crab meat. Takesushi chirashi had a small portion of eel surrounded by shredded omelet, two slices of pickled ginger, two slices of pickled lotus root and a slice of fish cake. A pretty measly combination for $8. The lunch box at Sushiko on Wisconsin Avenue has a dozen or so delightful little fish delicacies in various compartments, a much more ambitious presentation, and at a lower price. Thus, while much delights us at Takesushi, we'd skip the chirashi.

Nevertheless, at Takesushi it is clear that the fish of Japan are in good hands.