In America, theatergoers talk a lot about entertainment, and when the play is absolutely impossible, obscene, blasphemous, outrageous or dull, they tend to just quietly drop out at intermission.

In Ireland, they riot.

"Oh, there was some trouble at the very first, when Yeats and Lady Gregory opened their Irish Literary Theater in 1899," said Tomas Mac Anna, the director of the Abbey Theater, which last night opened a six-day stand in Baltimore's Mechanic Theater with "Shadow of a Gunman." But the first riot worthy of the name came in 1907, when someone used the word "shift," or chemise, in J.M. Synge's "Playboy of the Western World."

"It went on for a whole week," Mac Anna said. "The actors were just walking through it because you couldn't hear yourself think. People were shouting that no Irishman would ever murder his da and no village would shield him if he did. Synge got the worst press any dramatist ever got."

Even on tour in America in 1910, the Abbey players drew roars and rotten eggs in New York, Boston and Chicago because they were showing the Irish Americans, not the leprechauns and cheery tales they remembered from the old country, but the bloody realities. "The company was jailed in Philadelphia. Somebody called Yeats the Antichrist. Shaw accused the Irish Americans of being one of the lost tribes of Israel. Oh, it was exciting. We haven't had so much of it recently. The last American tour was 1976."

It's what happens when you have a truly national theater woven into the very fabric of a society. Sean O'Casey's plays about the 1916 Easter uprising and the War of Independence which started in 1919 appeared at the Abbey short years after the fact, while feeling still ran high.The program notes for "Shadow of a Gunman," O'Casey's first play, produced in 1923, reassured the audience that the off-stage shots and explosions were only part of the show and not renewed street fighting.

Already the Abbey has offered five or six plays related to the tragedy of Northern Ireland today, notably J. Graham Reid's dramas about people caught up in the conflict and a 1976 revue, "State of Chassis," which set them to shouting at the name of Bernadette Devlin.

"We sent up the IRA and all the factions," Mac Anna said."We even brought on the pope. But it was Devlin that caused the uproar. The next night one man called in to ask for 'two ringside seats.' "

The small square building at Abbey and O'Connel streets in the heart of Dublin has always been considered by certain people an anticlerical den. Militant Catholics accused Orson Welles of being a communist in his Abbey days. He retorted: "But I'm doing my best to become a capitalist . . . without much luck, in fact."

The Abbey's beautiful new $1.7-million theater has 628 seats with a generous 72-foot-by-28-foot stage. This is not at all like the original, which burned down in 1951 to the strains of "Keep the Home Fires Burning" (at the close of "The Plough and the Stars"). The first Abbey stage, converted from a mechanics' institute in 1904, measured 16 feet by 19 feet, and the fact is important because it was on this postage stamp that the style of drama in the Western world was revolutionized.

"It was just the opposite of what was popular at the time," artistic director Joe Dowling remarked to a reporter yesterday just before the opening in Baltimore as part of the inter-national theater festival, which lasts through Sunday. "On a stage that small, so close to the audience and all, you had to act naturally. No overacting. Realism. It's still part of our tradition. The plays too, they were very realistic."

Things have changed with television and state subsidies (the first, in 1926, for 850 pounds, saved the theater), but the realism prevails.

"The theater has been linked with the whole national movement," Dowling said. "To this day, English plays don't travel well to Ireland, though American plays are doing nicely -- 'The Man Who Came to Dinner' was one of our biggest hits ever. And Sam Shepard is popular. We've also done Chekhov, who fits in with our realistic style. And recently some Shakespeare."

Foreign plays are a new development at the Abbey. The repertoire is still mostly Irish, some in Gaelic. One important writer is Brian Friel, whose "Philadelphia Here I Come" made a splash recently.Bernard Farrow is a promising comic dramatist. But so far, the Brendan Behan of the struggle in Northern Ireland has not turned up, the one who can make that story blaze forever in the world's memory.

The Abbey veterans still mourn the old theater a little. You could hear a whisper in any part of the house, they say. It was so tiny that to get from stage left to stage right, actors had to run around behind the building through an alley. Many a Dublin drunk, encountering a druid or ancient king or Black-and-Tan soldier in that alley, switched to tea for life. The seats were famously cramped. If you were over six feet, you could get water on the knee from jackknifing yourself against the back of the seat in front of you. But nobody seemed to mind.

The Gaelic tradition, by the way, has been given new impetus by a folk theater movement, separate from the Abbey, which makes full use of the music that haunts this lovely language, adding dance and mime and sone to plays that rise straight from the hedges and green hills of Ireland itself.

". . .and not some story translated from an English source," muttered Tomas Mac Anna. "That would never do, you know."