PARIS - If the walls at 5 Rue de Fleurus could talk, they would speak volumes. Even before 1967 - when Jean-Claude and Jeannine Gramond took over this minuscule bistro that might well have served as the setting for A.J. Liebling's gastronomic splurges - the address had a sense of flair.
Gertrude Stein is said to have lived at some point in the tiny, two-story house in the courtyard now occupied by the Gramonds. Hemingway lived down the street.

One can chart the social and cultural changes that have overtaken the neighborhood since the day the couple opened their restaurant with five francs in the cash register and nothing more than a desire to serve simple, classic French fare. In the 1960s they often did two services at lunch, sending the overflow for a walk in the Luxembourg Gardens until places were liberated.

Before Francois Mitterrand became president of France, he lived around the corner, on Rue Guynemer, and was a frequent diner. The bourgeoisie of the neighborhood, including august members of the Academie Francaise, politicians, bishops from Rome, United Nations leaders and editors from the many publishing houses within a stone's throw of the Luxembourg made this their cantine. In short, the sort of place Parisians like to call an ''etablissement confidentiel.''

Today, the lace tablecloths, the bouquets of dried flowers, the fish tank in the tiny glassed-in terrace, are all testaments to days long past - another life, another style of cooking. And so is the dearth of ''clients fidèles.'' Publishing houses have moved to the suburbs, the two-cognac lunch is a relic of yesteryear and many of the intellectuals are now too old to make it out of their apartments to the Gramonds' domain. The younger generation would rather find nourishment at neighborhood cafés.

Chef Gramond's cuisine is both earnest and admirable. He makes twice-weekly, middle-of-the-night treks to the Rungis market for produce, meat and fish. They have always split the chores, he cooking out of a compact kitchen in the back, she tending to the 20 or so spots in the dining room.

One of a rare breed of chef left in France today, Gramond refuses to alter the classic cuisine he learned more than 40 years ago in the hotel school in Toulouse. The menu, handwritten and mimeographed in purple ink on the machine they bought three decades ago, is brief and to the point: You might find seasonal green asparagus from Provence bathed in a chervil vinaigrette; a commendable terrine of foie gras; plump scallops seared in butter and served on a bed of leeks; small, tender baby leg of lamb with a fine sorrel sauce.

Daily specials might include a lamb stew prepared with white beans, or haricots blancs, grown by Gramond on their farm in the Vosges. And come fall, his game specialties take over, with a delectable wild hare terrine; a civet de lièvre, and roasted partridge.

Three bulging cellars beneath the restaurant harbor treasures from days past:

A hoard of sturdy Santenays from the Cote de Beaune, dating to 1978, all priced at less than 400 francs. A charming 1982 Carmes Brion goes for 389 francs. There is an exceptional, long maturing Chasse Spleen, with the 1976 priced at 430 francs; as well as a 1975 Pierbone at 268 francs.

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THROUGHOUT the evening, the chef timidly enters the dining room in his clogs and spotless whites, awaiting each diner's opinion on his latest efforts. Later, come dessert time, he is back in his domain, and you hear the gentle rhythm of egg whites being beaten to stiff peaks, ready for his famed soufflé Grand Marnier.

So go, with a hunger for the fine classics of French gastronomy, and toast a chef who knows of what he cooks.

Chez Gramond, 5 Rue de Fleurus, Paris 6; tel: 01-42-22-28-89. Closed Sunday. Credit card: Visa. A la carte, 280 francs (about $45) a person without wine, including service; 350 to 400 francs with wine.