Oh, Barbie.

We know you're a yuppie now, with your own computer terminal, attache' case, copy of The Wall Street Journal and American Express Gold Card. But aren't you getting just a little too trendy?

Some 75 Barbie dolls went out in the past few days to "key members of the media in Washington and New York." They all had something they didn't come off the shelves with -- a black cape with the words "Chlamydia trachomatis" repeated around the hem in white letters, and a tag importuning, "Help remove the cloak of Chlamydia for 10 million Americans."

That's a venereal disease.

Oh, Barbie.

Of course, the tag doesn't actually say that you have this most common of all sexually transmitted diseases, but what does this do to your wholesome image?

"We feel," said David Leeper, partner in the public relations firm of Russom and Leeper, which dispatched Barbie via Federal Express on her anti-VD trek, "that we are morally justified in sending it out."

Leeper represents Syntex Diagnostics, which manufactures one of two new tests for chlamydia, which is twice as prevalent as gonorrhea and 10 times as prevalent as herpes. Women, especially, may harbor chlamydia without knowing it until it erupts into PID (pelvic inflammatory disease), which can result in sterility. Says Leeper, "It is, after all, the leading preventable cause of PID."

The black-cloaked Barbie -- the word "chlamydia" is derived from the Greek word for cloak -- was sent as an emissary to dramatize federal cuts in funds for chlamydia screening and to serve as an invitation to a press dinner to be held here next week in conjunction with the meeting of the American College of Obstetrics and Gynecology.

Leeper said the first call he got after distributing the chlamydia-Barbie invitation was from a United Press International reporter who called to decline the invitation and termed it "sexist and disgusting."

Leeper said the firm had used the doll before to attract attention from national women's magazines, and conceded that "one out of 50 editors was irate about it being sexist." He noted that although chlamydia occurs in both men and women, its symptoms are more often hidden in women, and the potential for permanent damage is greater.

A spokesman for Glamour magazine confirmed that the health editor had received a similarly attired Barbie doll in December, as an invitation to lunch at a posh Manhattan restaurant. "The lunch was even tackier than the invitation," said the spokesman. "After this elegant meal, they showed slides of diseased cervixes . . . "

But what does all this say to the 265 million little girls who have received traditional versions of this most popular fashion doll in the history of the world?

"Well," said a Mattel public relations representative carefully, "we really do care a great deal about protecting the Barbie image, and this really shocks us."

The representative said, "Nothing like this has happened before to my knowledge," but another Mattel source recalled that a few years ago "some skin magazine" had published a pornographic sequence using Barbie and Ken, her longtime fiance'. "The company decided to ignore it," said the former Mattel employe, "rather than call attention to it."

Spencer Boise, Mattel's public relations director, said he had been unable to reach the company that was using the dolls, but affirmed that "this is not an authorized use."

But most outraged by this use of Barbie is the doll's true mother -- Ruth Handler, who with her husband Elliot founded Mattel and conceived, designed and marketed the dolls. Barbie and Ken were named after their own children.

Ruth Handler, retired from Mattel since 1974, now operates her own business in Los Angeles. "It is," she snapped over the telephone yesterday, "just horribly offensive. I'm no longer connected with the company, but I feel a tug. Barbie represents an awful lot of good things, and I'm finding that it was an even more important part of young ladies growing up than I ever realized.

"A child's plaything should not be subject to this kind of violation," she said. "I'm sorry about all those people being sick, but they shouldn't use a child's toy for a marketing scheme.

"There are just some things you shouldn't violate."