WE ARE witnessing the nationalization - and some would say the homogenization - of Albert Innaurato.

The critics loved him in New York. "The new hot playwright in town," said one. "An original, of incomparable imagination," decreed another.

His "The Transfiguration of Benno Blimpie," a rather bizarre one-act play, was as successful as bizarre plays can usually hope to be. His full-length comedy "Gemini" - much less bizarre - is a Broadway hit. Now it's at Arena Stage too, and soon it will appear in Los Angeles and Seattle. His script for "Verna: USO Girl" - not at all bizarre - was applauded throughout most of the country when it ran on PBS in January.

But Innaurato, 29, shrugs off practically anything that's said about him. He talks as if he's just a regular guy trying to do a decent day's work.

Watching a dress rehearsal of "Gemini" from the back of Arena's Kreeger Theater the other night, he bobbed from heel to heel, took notes, still found some of the jokes funny after all these months, and occasionally muttered something like "sluggish."

In discussions with director Douglas Wager, it was Innaurato who wanted to cut some lines out of the script. Speaking to the actors after the rehearsal, it was Innaurato who urged them to lighten up, to "not be afraid of being a little superficial." Answering questions from the audience of Arena contributors after the show, Innaurato denied any concern about the "universality" of "Gemini" or its potential for classic status.

"I don't think playwrights write for posterity," he told the crowd. "The reason theater is dying, or is a dead art form, is because of the 'masterpiece' point of view. It doesn't have to be a great work for you to enjoy it. If a playwright sits down to write a masterwork, he or she becomes paralyzed."

What's this? "The new hot playwright in town" thinks the theater is dead? "Commercial theater is dead," said Innaurato, swigging a soft drink backstage after the show. "There may be some kind of answer in regional theaters and small-scale theaters."

Most playwrights, of course, would kill for the sort of commercial success "Gemini" has experienced. The dilemma of Francis Geminiani, who realizes that he is less attracted to his rich girl friend than he is to her brother when they visit him at his South Philly home on his 21st birthday, has tickled Broadway audiences for nearly a year. Innaurato has also given Francis a quartet of colorful neighbors and relations whose antics and eccentricities seldom fail to provoke raucous, high-priced laughter.

But one hit has not convinced Innaurato that Broadway is hospitable to new playwrights. He regards the "Gemini" run as "a miracle." When called upon, he can recite the traditional story of the suffering young playwright as well as the next guy.There was a period when he was indigent, evicted and hospitalized. With "Gemini," said Innaurato, "I know how lucky I am and how bordering my success is." His most recently produced play, "Ulysses in Traction," was an off-off-Broadway failure, and Innaurato figures he has one more chance to ride on the success of "Gemini."

"Reputations have a high mortality rate in the theatre," he said. "The American arts scene is the cruelest, most irrational in the world. Most critics and theatre writers are baboobs, yet they make or break you. Even if people know a critic is an idiot, they still wait to see what he thinks." Maybe because ticket prices are so high? Well, yes, it's the whole "hit" structure that condems so many plays, Innaurato agreed.

"It isn't just the reviewers. Everyone makes mistakes. God makes mistakes. Look at my life," Innaurato laughed.

This may not soumd like a happy man speaking. But Innaurato is as serene as a swami compared to the characters in his plays. Do not compare Innaurato to his characters, however. Despite the fact that he shares with Francis of "Gemini" a blue-collar South Philadelphia background, an astrological sign, a self-acknowledged "food fetish" and a devotion to Maria Callas (last week he won a game of "opera jukebox roulette" at A.V's, the Italian restaurant with an operatic sound track in downtown Washington), Innaurato resists any efforts to tag his work as autobiographical.

Still, it's hard not to notice that of Innaurato's publicly successful works so far only "Verna: USO Girl" was set outside the Italian-American South Philadelphia milieu. "Nabokov wa asked what constitutes good writing," he told the Arena audience, "and he said 'detailed writing'. I know Philadelphia well, and those details are important."

"Verna" was not nearly as rewarding to him as a writer as his stage works are. "It was a professional job," he said. "Most TV writers are glorified secretaries." Yet it was probably seen by more people than the rest of his work put together. Its success must be tempting, for despite Innauroto's disdain for the commercial theatre, he wants to communicate with as many people as possible in his work. On Broadway, he has been "very surprised at some of the people who come to see 'Gemini'. They call and ask how many shows there will be tonight. Obviously we're attracting people who don't go to the theatre very much."

This is fine with Innaurato. He said he has nothing but respect for Neil Simon, that most accessible of American playwrights. "Your duty is to please the audience so you can communicate with them," said Innaurato. "This is not to say you have to write for a 12-year-old mentality. Audiences are not stupid. They catch more than elitist pundits realize."

The Arena audience, said Innaurato, "seemed very intelligent," and the production "takes the play more seriously than the one on Broadway." Which is why he felt free to tell the actors to "speed up, get louder, go for the laughs. When the work is already good, you can say that without turning them into cartoons." He suspects "Gemini" might go over even better in cities with large ethnic populations.

Innaurato may be another test case of the theory that America now has at least two theaters - New York's and the rest of the country's. His work was developed almost completely within the New York nonprofit theatrical world and its Connecticut adjuncts, the Yale Drama School and the O'Neill Theater Center's National Playwrights Conference. New York critics put him on the map. He could be a Preston ("Texas Trilogy") Jones in reverse - a playwright who has a hard time crossing the boundary. On its way to Broadway success, "Gemini" was rejected by "practically every regional theatre in the country," said Innaurato. Arena turned it down for inclusion in the In the Process series a couple years ago.

It's hard to think of a playwright who has repeatedly reached a national audience since Tennessee Williams, said Innaurato. His colleague David Mamet, for example, is "a made-up playwright," according to Innaurato: "I like him personally, but compare what he has done in three years - mainly a string of one-acts (primarily successful in New York and Chicago) - to what Williams did" in his first three years on the national scene. Of dourse, musicals usually span the country, Innaurato noted, because of their songs and albums and other paraphernalia. But apart from Neil Simon and musicals, you never know what's going to play where. "It's always a primeval forest," said Innaurato.

As Innaurato ventures into that national theatrical forest, it will be a challenge to keep sight of his own South Philly roots, to reach a national audience without sacrificing his distinctive identity. Innaurato appears aware of that challenge. The failed "Ulysses in Traction" was set at a university working on "Aggy's Back," to South Philadelphia after years of living in the South. Innaurato's back, too.