A few months into her total immersion in the work and personality of Gertrude Stein, actress Pat Carroll began to notice personality changes.

"I knew something was happening when my children told me, 'Mom, you're repeating everything three times.' Then I noticed that I was not using contractions very much when I talked -- there are no contractions at all in the first act of 'Gertrude Stein Gertrude Stein Gertrude Stein.'"

"As an actress," Carroll admits, "I was quite selfishly using her. You want to bend a character to your own strengths and purposes, you know. But I think she bent me."

Now that she has finished her 14-month run in New York and had some vacation time, Gertrude Stein is back in perspective and Pat Carroll is Pat Carroll again -- a tough, bright and witty personality in her own right.

She has taken here one-woman Gertrude Stein show on the road, using a 30-foot mobile home "because some of the places where I'll play may not have a decent dressing room, and I want to carry around my own environment." She and Gertrude are booked solid through May -- mostly at college campuses -- after she finishes her stay at the Arena Stage. To open here next season, she is deliberating among bids from London, Paris, Chicago, Los Angeles and a few other major cities, "places where they want us to settle down for three or four months."

A veteran actress who has been a regular on television since the "Red Buttons Show" in 1952 and who had a steady role on the Danny Thomas show. Carroll has appeared in many television dramas ("Kraft Theatre," "Producers Showcase," "Policewoman," "Interns," "Police Story"). But she may be best-known for her work on game shows such as "What's My Line," "Password" and "I've Got a Secret." For 10 years, she was a regular in the annual television production of Rodgers and Hammerstein's "Cinderella."

She won an Emmy for her work in "Caesar's Hour" and a Tony nomination for her Broadway appearance in a short-lived 1955 revue called "Catch a Star." Her credits in the classical theater range from "The Rivals" and "Threepenny Opera" to Dylan Thomas' "Under Milk Wood."

She sums up her career with a quote from her grandmother: "They pay you for getting up there and acting silly?"

The inspiration for the Gertrude Stein show arose five years ago, as Carroll was preparing for grandmotherhood herself (her three children are ages 13, 21 and 22). Knee surgery put her temporarily out of action, and she began thinking about doing a one person show.

In 1975, she recalls, "Joe Namath and I were both out of the fall lineup.

I became restless, unhappy, morbidly obsessed with having to create my own theatrical activity. Very few producers were beating the bushes for aging, overweight actresses with a limp."

During her months in bed, she began running over a list of possibilities, and Gertrude Stein kept popping into her mind, although she had never particularly enjoyed Stein's writings. "I read Stein in college," she says, "and I built up a lot of aversion to her. Now I run into the same kind of resistance from my friends -- before they have seen the show. They expect it to be boring. Why would I want to be boring?"

For a while, still convalescing and half-buried under a mountain of books by and about Gertrude Stein, Carroll tried to write her own script.Then she confided her project in a young playwright she knew, Marty Martin, whose main problem was that his scripts tended to be about four hours long.

She commissioned him to write a script, which eventually came out about three hours long, and worked at cutting it in half while she took other jobs (a road tour of "Pippin," then a movie, "The Last Resort"). The discarded material may eventually be made into a musical sequel, she says, more than half-joking.

"Before I started," she says, "Julie Harris, who has a lot of one-person-show experience, told me I would have to work very closely with the playwright.

"You know, there are certain things every actress wants to do -- a mad scene, a drunk scene, a scene of quiet melancholy -- and I was able to ask for all of these. I didn't tell Marty how to write or what to write, but I gave him my reactions: 'I'd love to do that,' or 'I'm scared, but I'd like to try.'"

One inkling of the kind of audience reaction she could expect came when she called her mother and told her she was going to do a show about Gertrude Stein. "That's nice," her mother said and ended the conversation, but later she called back with a distrubing question: "Wasn't Gertrude married to Jule Stein?"

Carroll says she wants audiences that will come in without too much advance knowledge. "The show isn't for scholars, critics or experts. They would have packed the house for four nights, and that would have been it." But she does attract a lot of Stein fans, and she is surprised at how many there are: "We have truck drivers and housewives coming in who are devoted readers of Stein's work. But my own interest is not so much in her work as her life and her city -- Paris in the '20s."

Nonetheless, Carroll is planning to branch out. "By 1985," says the enthusiastic newcomer to the one-person show tradition that runs from Charles Dickens through Hal Holbrook to most of the people who play at Ford's Theatre, "I hope to have a trilogy -- portraits of women from the 15th to the 20th centruy, beginning with a Spanish woman and ending with Gertrude Stein.

"Then I'll be able to do three roles in repertory, one after another through the week, and have a little more variety in my work." She would rather not name the other roles -- why give ideas to the competition? -- but her enthusiastic description of her Renaissance Spaniard could only apply to St. Teresa of Avila.

"You guessed it," she admits. "What a woman! In today's society, she could have been a president of some corporation like IBM."