Rex Harrison has changed.

But it's not just him.

"It has changed," he says, "I have changed and quite possibly 'they' have changed.

"There was a period in the '50s and '60s when life seemed to have a different pattern," he says. "Things have become so much more real and sterner than they were. I have a small circle of friends how but not a whole bunch of people I don't really care about."

In the '50s and '60s Rex Harrison, actor-superstar, gallivanted around the world, traveling in Rolls-Royces and yachts, hobnobbing wiht royalty, partying with the rich and famous, marrying other superstars appearing in the gossip columns. It was most as if one real more about his extracurricular activities than his extraordinary professional ones.

"The world was a rather different place then," he says. "The distribution of wealth has changed a lot. A lot of people in my Portofino days had yachts. Life has changed so much - especially in England. The leading actors in those days, in the 'Fair Lady' days, were lionized by society. That doesn't happen anymore.

"American society has changed as well. The money isn't so lavished. I don't see the people I saw then. For example: It was marvelous, tremedously generous of people like Michael Phipps and Jock Whitney to loan me their country houses and their boat houses in Long Island when I was doing 'Fair Lady.' Now Jock Whitney isn't very well and Michael Phipps, I think he may well be dead. Palm Beach you know.

"I keep very much now within the group of the theatre, and in films, the arts. I do find now that people outside the theatre don't really understand our trials and tribulations and agonies - and they are quite hard to have long conversations with. THeir interests are so different from mine. Maybe this whole thing of wanting to be with people of mutual interests is a trend.

"People who run about, gadabout nowadays, are rather anachronistic and sad. They're empty, unhappy people."

Rex Harrison is 68 and there is about him a mellowness, an absence of urgency, a relaxed, unhysterical quality which comes with age. He's easy to be around, fun to talk to, more fun to laugh with.

He opened Monday night in George Bernard Shaw's "Caesar and Cleopatra" at the Kennedy Center with Elizabeth Ashely. The reviews indicated strongly that the play needs more work before it hits New York in three weeks.

Harrison seems not in the least upset; he's relaxed in fact, in the matter-of-fact way of a professional, who knows, as Harrison himself said, "There's lots of work to be done."

He is dressed in a soft gray suit, very understated very subtle, very continentual. He has the kind of courtly manners that younger men today don't have, and in those manners is an attitude about women which is no longer fashionable. The kind of attitude, in fact, which may have been responsible for his latest divorce from Elizabeth Harris.

Rex Harrison has been married five times. To Noel Thomas; Lilli Palmer; the famous marriage to Kay Kendall, who died of leukemia two years later; Rachael Roberts, and most recently to Harris, 29 years his junior.

In "Rex" his autobiograph, published in 1974 and dedicated to Elizabeth, Harrison wrote:

"I do reget one major misconception. I had always believed that actors should be married to actresses. Absolute rubbish - actors should be married to wives. Of course I am lucky that Elizabeth has always been mixed up in the threater and studied at the Royal Academy of Dramatic Art for some time.

"She has quite definite ideas about what she likes and dislikes in the theater and those feelings happily coincide nearly always with my own. But I am happier still that she decided early on to give it up and is not ashamed to have 'Housewife' written in her passport. She is a mother as well as a wife and I love that side of her too. She adores her sons and I enjoy watching her adore them."

He is reminded of this passage. He chuckles, looks down at his graceful hands for a moment, then looks up with a twinkle. "That chapter was written before my marriage broke up. I don't really want to go into marriage as an institution," he pleads.

Rex Harrison has changed.

"Marriage," he says simply, "can ruin things. Elizabeth and I are still great friends. But evidently marriage doesn't really suit this extraordinary female trend of independence and the general swing of women's rights."

He seems a bit puzzled, but he's trying to understand.

"They feel trapped.That certaintly happened in my last marriage . . . the winds of change . . ." he murmurs."

"It doesn't apply to all women. Maybe it's just a special thing with women in the arts," he ponders. "I can't believe the whole of the middle classes in the modern world have the same problems." This is almost a question. Then a look of incredulity comes upon his face. "Could it be creeping up? I suppose it is. I know that now. It's maddening, of course."

There are, he admits, other factors. Children, for instance. "They make it difficult. In the case of Elizabeth, she had three children. I've had a couple, so I know. Children," he says again, "Are very difficult."

But Harrison doesn't seem to be pining. "I find my life is marvelous," he says brightly. "I like being independent. Of course, I would prefer to have a woman in my life."

He stops. Does a double take. Realizes that's a Henry Higgins line from "My Fair Lady."

"Don't put that in. Leave that out," he laughs, waving his arms in surprised embarrassment.

"Work, he says, changing the subject," is a great stimulant."

The lunch is brought up to his hotel suite. The table arranged. Navy bean soup and smoked turkey and ham. He rubs his hands together and sits, waiting politely to begin.

"I adore food," he says. "I don't cook but I've always been fortunate to have someone who cooks for me." A sip of soup. "Ummmmmmmm. Delicious soup. You know. I'm rather fond of women who like cooking. There's nothing more attractive to me than having women cooking a lovely meal, being with it while it's being cooked. And I love this new thing of eating in the kitchen. In the old days when everyone had cooks it was their domain. You couldn't go in the kitchen to cook an egg. That's one great salvation of not being able to get domestic help these days."

He likes this new informality he says. "I like it very, very much. I prefer it, in fact. People I'm sure think I lead a much grander life than I do.

One wonders whether he has changed his mind about actors marrying actresses. "I want a rain check on that," he chuckles, a bit sheepishly. "It is difficult for men and women to be husbands and wives in the same profession. There's the competition, one is more successful than another. It causes friction. On the other hand, it's fatal to be married to someone who knows absolutely nothing about the theater."

Harrison thinks women in theater have a harder time when they're not working than do men, though he admits that having a fallow period is very difficult for anyone.

"For some reason it's harder for women to replace their work with something. Especially if they haven't got a home, though things have changed. It is a side of women however much they deny it: they need and want a home and children. It's the anatomical function of women and lots of actresses I know do become quite frantic when they're not working."

Being out of work is not unknown to Rex Harrison, nor is being down and out, having bad reviews, having disappointments. And it still amuses him when people see him as a great superstar, a man who has everything, the great REX.

"It's very strange," he says. "On the outside one forgets that the hills and valleys go on all the time, that there is the private side and the public side.

So remember thinking the same thing, though, when I was a young actor meeting other famous actors, that they had it all.

"Then I remember later meeting them and having them tell me that when we met they were having a terrible time, that they were having a bad patch. But it happens to everybody, that's what's interesting. I remember going to Hollywood, meeting all the great stars and playing golf with Clark Gable. Here he was the greatest star and he spent the whole time grumbling about Metro and how they were giving him all the wrong parts and the movies weren't any good. And it was not so long after the terrible tragedy with Carol Lombard. A man couldn't have been more depressed.

"Being famous and having success really enables one to do things one wants to do, but I've had lots of depressions, many little ones. I would think probably the worst one was after a disastrous play in London and then a period after that when I was out of work. Right before I met Elizabeth." Then his face brightens. "But I've been working awfully hard in the last year."

Harrison looks at his watch and gasps. "Good god, I'll be late for rehearsal." And he jumps up and grabs his coat, his wooly scarf and his shape."

He has been rehearsing 12 hours a day, and this will be another day of rehearsals before another night of performance.

He beams. "It's discipline. It's a feeling of responsibility to the people who come to see you. It's like being a boxer. One has got to keep in tip-top.

He hasn't changed that much.