Twenty years after Neil Simon came up with "The Odd Couple," one of his biggest Broadway successes, he has come up with "The Odd Couple."

Granted, it may be a new version of the comedy that switches the sexes of all the characters in his original script, so that Felix Unger is now Florence Unger, Oscar Madison is Olive Madison and the daffy Pigeon sisters from England are the laquered Costazuella brothers from Spain. But it's the old Neil Simon at work, joke-a-minute Simon, who seemingly can no more resist the impulse to paper the stage with wisecracks than an elephant can pass up a peanut.

This is likely to be welcome news for a large segment of the theater-going public, which, lured by the further promise of Sally Struthers as Florence and Rita Moreno as Olive, has only to dart off to the National Theatre, where "The Odd Couple" took up a four-week, pre-Broadway residence last night. Still, coming on the heels of Simon's largely joke-free "Brighton Beach Memoirs," which just vacated the National, the current show can only be viewed as a step backward.

It's not that "Brighton Beach Memoirs" wasn't funny, or, for that matter, that "The Odd Couple" isn't funny. But "Brighton Beach" was painted in warm, human colors, and its humor was rooted in what for Simon was a fairly subtle appreciation of human psychology. "The Odd Couple" is a broad, brash cartoon, content with such easy quips as "If you had two more legs, you'd take yourself dancing" or this observation, inspired by a filthy refrigerator: "I saw milk standing in there that wasn't in the bottle."

Given the changes wrought in society by the women's liberation movement, it must have seemed both a logical and timely idea to make a pair of women the odd couple, throw them together in a six-room New York apartment and let them get on one another's nerves, just as their male counterparts did. Abandoned by her mate, fastidious Florence moves in with slovenly Olive, who is already paying alimony to her ex-hubby. What wrecked their marriages, presumably, will put their friendship to a severe test. But while Simon has altered all the pronouns and even rewritten large patches of dialogue to accommodate the circumstances, the comedy doesn't look appreciably new nor does it offer any particularly revealing insights into the female psyche. Frankly, it looks rather like the same old comedy, only in drag.

There is even something vaguely exploitative about the evening -- akin to David Merrick's decision, midway through the wildly successful run of "Hello, Dolly" nearly two decades ago, to put an all-black cast in that musical. That patronizing, albeit lucrative tactic, capitalized on the then-burgeoning black liberation movement in the way that this "Odd Couple" tries to appeal to today's feminism. Less than a breakthrough, the show at the National is, one suspects, entirely too craven to be just an innocent entertainment.

Both Moreno and Struthers appear to be auditioning for a television sitcom, understandable in Struthers' case, since she has a long history on "All in the Family" to live up to. Looking rather like Ethel Merman's blond sister, Struthers gives the more amusing performance, as the compulsive fussbudget who puts doilies on the seats of chairs, washes the telephone cord and generally carries on like Mr. Clean and Betty Crocker rolled into one. Her role is better, but that's not all of it. The actress is considerably fleshier than she was in her salad days on TV, and her squeaky ditsiness seems to have gained a certain comic ampleness as well.

Playing the slob in this two-woman sorority house, Moreno is going against all her natural qualities. Lithe and handsome, she has an inbred feistiness that suggests she could take on the Greek Furies and emerge victorious. A fussy roommate hardly seems like much of a challenge for her. The script doesn't arrange matters, either. While it wants us to believe that by day Olive is a savvy and successful writer for a New York TV news show, it pretends that by night she is incapable of rustling up a date on her own. The idea of Moreno turning all moist and giddy at the prospect of the Costazuella brothers coming for dinner just doesn't wash.

Those brothers (Lewis J. Stadlen and Tony Shalhoub) are "two classy Spanish guys, no taps on their shoes," who speak "perfect English every once in a while." The dinner is not one of the whiles. They confuse "no good" and "nougat," say "steal the cake" when they mean "bring home the bacon" and sow panic in Struthers' eyes when they ask for "a screw" -- a corkscrew, of course. Exploiting the linguistic and cultural barriers, the scene is as obvious as it is protracted. Neither Stadlen nor Shalhoub transcends Simon's facile stereotyping.

If you are looking for one thoroughly believable performance, I advise you to focus on Mary Louise Wilson early in the evening. One of the four women who drop in on this harried household for a weekly poker game, Wilson plays a no-nonsense cop, takes all the jokes in her no-nonsense stride and alone manages to suggest that this production might have a rationale, not just a gimmick, going for it. In the punched-up climate induced by director Danny Simon, the playwright's brother, that is no small accomplishment.

Not being deaf, it would be folly for me to deny that Simon churns out the laughs thick and fast at the National. By the same token, I can't shake the impression that this "Odd Couple" is really not so many steps removed from the demeaning spectacle of lady mud wrestlers. Both use women and give them precious little in return.

THE ODD COUPLE. By Neil Simon. Directed by Danny Simon. Scenery, David Mitchell; costumes, Ann Roth; lighting, Tharon Musser. With Rita Moreno, Sally Struthers, Marilyn Cooper, Kathleen Doyle, Jenny O'Hara, Tony Shalhoub, Lewis J. Stadlen, Mary Louise Wilson. At the National Theatre through Feb. 17.