Hours: Sunday through Thursday, 8 a.m. to 11 p.m.; Friday and Saturday, 8 a.m. to midnight.

Atmosphere: Casual and comfortable.

Price range: Sandwiches from $3.95, complete dinners up to $11.95.

Reservations: Not required.

Credit cards: American Express, Visa, MasterCard.

Special facilities: highchairs; accessible to wheelchairs through the kitchen; usual Georgetown parking problems.

When Jack Kennedy was president and I was a timorous freshman in college, Martin's Restaurant was the perfect place for a youth out in the world for the first time.

Small, decorated with lots of polished wood and dark old prints, it was different from the glittery eateries opening up to serve the New Frontiersmen or the raucus hamburger joints nearby serving generations of Georgetown University students. It had a class a youngster could understand.

The pleasure then was to bundle up on a raw Saturday morning and march through Georgetown to Wisconsin Avenue, past the stylish homes, the gayly lit parlors of the rich, and enter the cozy quiet of a restaurant where the price was always fair and the food good enough for Momma's approval.

Martin's has remained remarkably unchanged, or so it seemed one recent evening when all of us trooped in for a family feast. Even the waiters appeared to be the same gentle souls who had so patiently served us, and the menu selections haven't changed at all, except that inflation has driven up the prices.

It was comforting to be back. The 80 seats were filled as usual with families, elderly people, students in groups and alone, bookish tweedy types and quiet couples. A football game quietly flickered over by the 12-seat bar and the green-jacketed waiters worked noiselessly through the hall.

The oysters are still outstanding: plump, juicy and succulent, trucked in every day from Long Island. At $3.25 a half dozen they are without doubt among the best available in this city. Likewise, the cherrystone clams ($2.95 a half dozen) from Crisfield are sweet, tender and flavorful.

However, the lobster bisque was nothing more than a tomato-ey concoction too heavy in flour and far too light in lobster. On the other hand, Manhattan clam chowder was a nice vegetable broth that actually had pieces of clam in it, even though it lacked adequate spicing. And crabmeat cocktail ($4.95) was packed with fresh, tasty backfin crabmeat.

The entrees were just as unpredictable. Seafood Norfolk ($10.95) was nothing more than a smallish chafing dish filled with four shrimp, four scallops and two small puffs of crabmeat, all swimming in an unsavory and watery base. Shrimp scampi ($9.95) was about the same: seven smallish shrimp floating in a weak and watery garlic broth.

Crabcakes ($9.95) were a good-sized but uninspired commercially prepared dish brought in frozen and zapped hot in the kitchen. They were long on filler but short on crab, unhappily spiced, and utterly lacking the crunchy texture of a well-made crabcake.

Prime rib, however, was superior, a not-over-generous but adequate cut of prime rib cooked exactly to order and accompanied by a baked potato, a really fine cole slaw and a house salad ($11.50). But rainbow trout ($8.50) was too fishy, too frozen, too far from what trout is all about.

A smallish salad accompanied each entree, along with a tasty side dish of cole slaw. The house salad dressing, however, was a creamy Italian mess that came in a soup bowl and was thick from too much flour.

The kids were smart enough to order from a small but excellent sandwich offering. The bacon cheeseburger ($3.95) couldn't have been made better at home, and the hot pastrami and Swiss cheese on rye ($3.95) tempted all the adults at the table. Milk was expensive at 75 cents a glass, however, given the small size of the glasses.

Desserts, oddly enough, were excellent, especially the cheesecake and a truly worthy carrot cake (both $2).

Service was good, and there is a certain charm about the old place, to say nothing of the oysters. But in the future, our plan for eating at Martin's will be to stick to the shellfish and desserts and save the big bucks for somewhere else.