The play that won last year's Pulitzer Prize, "The Gin Game," has two characters, one theme, one joke and a few wispy points. With Jessica Tandy and Hume Cronyn playing the two characters, as they do at the Kennedy Center, did on Broadway and on tour and soon will do in London, the theme seems fresh, the joke is funny every time, and the audience is willing to assume and help supply importance to each slight suggestion of meaning.

Emptiness in old age is the theme. The two characters are residents of a nursing home, the sort of place at which "if you live long enough, sooner or later you end up," as the old man says. He describes his condition as "one of the most advanced cases of old age in the history of medical science. The mortality rate is incredible."

The joke is that although he calls himself a gin rummy expert, he can't deal without counting aloud, and she easily wins every game. And the points, just barely hinted at, are that old age brings, in addition to boredom, isolation, ruinous medical bills and the curtailment of independence.

"The Gin Game" was a Broadway hit before "On Golden Pond" opened, although Washington saw the latter first, and perhaps owes its distinguished recognition to the fact that it is about the long neglected subject of aging. But the "Gin Game" characters seem in comparative health, their isolation from spouses and children was their decision in earlier life, they have a minimum of comradely feeling for each other, and while they are embarrassed to be secretly taking welfare, they are adequately housed and fed. "On Golden Pond" did not show financial problems, but it dealt in a more complex way with the effects of illness, family relationships and energy limitations in old age.

"The Gin Game" is about an old age in which one can only hold on to meaning through shuffling and re-dealing the same cards. When there no longer seems to be an element of chance, the man can't go on. The only alternative activities available seem to be watching television, discussing funeral arrangements and "being amused" by magicians, choirs or "that bunch that came looking for substitute grandparents." One must conclude that their younger lives were equally empty, but that this was disguised for them by the variables of daily life.

The high naturalistic acting of Tandy and Cronyn carries all that inactivity and repetitive dialogue, and even makes these dry figures appealing. Her emotionally tight old lady is so effective that it is a shock to catch a glimpse, now and then, of the actress' beauty. His step, as he tries to rush to her side but can't, is full of meaning. And unless there is a concealed lighting trick, he also manages the greatest feat since those child actors who used to be able to cry on cue: his face turns red on cue.

But although the two have received honors for this production, the Pulitzer went to D.L. Coburn's script, which means it ought to have some life of its own after this masterful team leaves it. The thought of its being done by lesser actors, let alone amateurs, or teen-agers with cornstarch in their hair for the high-school play, is ridiculous, as is the prospect of anyone's being able to sit down and read it through.

And yet at least some of these pleasures ought to be available from a work that has been certified as representing our highest standard of dramatic literature. THE GIN GAME - At the Kennedy Center's Eisenhower Theater through May 12. CAPTION: Picture, JESSICA TANDY AND HUME CRONYN IN "THE GIN GAME."