Nineteen seventy-eight was the year of the status jeans.

Slit skirts, strapless tops and stiletto heels may have attracted attention again this year, albeit in a new way. But status jeans, with a designer label prominent on the rear pocket, are strictly an invention of 1978. And a hot sales ticket as well.

The new jeans have little in common with the 1960s work-clothes, back-to-roots attitude in dress. They have evolved beyond their origins in the same way that pea jackets grew out of navy uniforms, or that sweat shirts came to be created in cashmere.

The status-jeans phenomenon demonstrates American designers' special genius for taking a style that is flying high, rearranging and redesigning it, and marketing it brilliantly into big bucks.

At $27 to $40 a pair, jeans are no longer made only of denim, though that is still the most popular fabric. There are satin and silk, linen and canvas, velvet and corduroy. And this fall, leather as well.

They boast labels including Calvin Klein, Gloria Vanderbilt, Geoffrey Beene, Ralph Lauren, Cacherel, Maurice Sasson, Yves Saint Laurent and Pierre Cardin, with Scott Barrie, Thierry Mugler, Stephen Burrows, Bill Blass and many more still to come.

"We were optimistic when we first signed a contract to put our name on jeans," says Calvin Klein's business partner, Barry Schwartz. "But wow, we had no idea what was going to happen."

What did happen, Klein says, is that they started selling fast the minute they hit the stores, and are now being turned out at the rate of 50,000 pairs per week. Klein's jeans are made by Puritan Sportswear, which has bought the factory which first contracted to make the jeans. The company expects to push out 100,000 per week.

"It's our best license," says Klein, who is amazed that his jeans have surpassed even his menswear sales -- which amounted to $35 million this year.

Ellen Saltzman, corporate fashion director of Saks Fifth Avenue, says Calvin Klein's jeans clicked "because they were the right status at the right time." The good fit, narrow leg and inherent security and prestige of the Klein signature made them "incredible," she says.

Fit is apparently the main attraction. "Regular jeans don't fit properly at the waist," says Calvin Klein jeans wearer Marilyn Funderburk. And "the clincher," she says, is "that they don't cost that much more than regular, ordinary jeans."

Geoffrey Beene says he started to make jeans after two round-the-world business trips this year. "At every airport I saw tons of people wearing jeans," said Beene. "It was clear there was a big market for them."

"I found myself spending hours looking for jeans that fit well," says Gloria Vancrbilt. "I finally got tired of this and decided to design some, since I was sure that if I had this problem, others would. too."

Joe Cecala, vice president of sales and marketing for Vanderbilt jeans, says 700,000 pairs have been sold since last January.

At the moment, designer jeans are such big business that Bloomingdale's has created a department called "Pure Jeanius," and similar departments have opened in stores across the country.

"It's the label cachet and the chance for customers to get a designer label at a fairly reasonable price," says Kal Ruttenstein, fashion director of Bloomingdale's. Ruttenstein isn't sure precisely when the jeans "took off," but he figures it was right after he returned from seeing the new collections in Paris in November. "And it all happened so fast we didn't know what hit us," he says. He's convinced that status jeans will be around for a while, but wouldn't hazard a guess as to how long.

Women of all ages are buying the jeans. The more conservative are sticking to the 17-and 18-inch variety (measured at the hem), while the more avant garde, and particularly the younger customers, prefer the narrower versions. There are also totally skintight, stretchy Lycra jeans a la "Grease" now being made by DBA of California and Giorgia Sant' Angelo.

Men are buying fewer than women, but they have had less of a hance: fewer varieties are available to them. Cacharel is currently the frontrunner with his straight-leg jeans. The Beene cut is more full. Izod has just gotten on the bandwagon and will have their jeans at Garfinckel's shortly. Calvin Klein will add jeans for men in February.

"Jeans are such a totem of American culture," say Caterine Milinaire and Carol Troy in their update of "Cheap Chic," "that they inspire that kind of mania for the marginal differences, for the tiny details that will set you off from the crowd, set you apart from the blue-legged masses."

If Americans have a reputation for marketing styles the French are known for making them tighter, sexier and more expensive. When the Italians and French started making jeans more than four years ago, they struck out for the snuggest, sexiest look they could achieve. MacKean and New Man in France, Fiorucci and Jesus Jeans in Italy, distinguish themselves with a skintight fit across the derriere and down the leg.

"French-cut jeans became popular in America when Americans realized that the sexy, tight fit was worth suffering for," says Paul Guez, head of Sasson, a New York-based company which makes some of the skinniest jeans in the stores. But you only have to suffer an hour at a time, he insists: the first hour you put them on, and an hour each time they are washed. After that they are comfortable, he says.

Sasson jeans are named for an imaginary soul, insists Guez. "The word 'sasson' means happiness in Hebrew," he says. And he claims that Maurice Sasson is a name he made up.

"Not so," says Maurice Sasson, 27, who started the Sasson house four years ago and claims to be the originator of the Sasson jean. Though he lost the use of the brand name in a legal battle with Guez, he has created a new label called Maurice Sasson, also in New York, and has taken his jeans to the very narrow 12-inch width, "just wide enough to fit over the boot," he says.

Sasson himself wears Levis. "Let's face it," he says, "they are hard to beat at almost any price."