Depending upon the press release, jeans are hot - or they're not.

People who say "they're not" point to a recent study by Jeanswear Communications, which shows that total jeans sales in 1981 were 502 million, but that figure gradually declined to 387 million in 1989.They further point out that VF Corp., the company that markets Lee and Wrangler jeans, closed four jeans factories last year.

But denim manufacturers say jeans are still hot. They have figures of their own. They point out that the average American teenager still buys four to six pairs of jeans a year.

It's a fact that the biggest fans of jeans are young people between the ages of 14 and 24. But since that group has been shrinking over the past decade, so have the sales.

According to Alan Millstein, publisher of Fashion Network Report, jeans don't seem to be fitting into the lives of the "thirtysomething generation," since this group is confronting the flab of middle age.

But manufacturers feel confident that the market will improve in the '90s. And they're bent on providing a better product, better service and better marketing.

Last August, the Lee Co. launched a new ad campaign and directed it toward the largest growing consumer group - women ages 25-44, with emphasis on the 30-year-old working woman and mother. According to a nationwide consumer research study, women account for 82 percent of all jeans purchased.

To attract more sales, jeans are now manufactured in a variety of styles and washes to fit anyone's fanny or fancy.

Joe Pacifico, vice president of marketing for the Lee Co., said, "We have determined through our consumer research with women across the country that the single most important factor in purchasing jeans is how they fit - both physical fit and how they fit their lifestyle."

Gap, for example, offers such options for women as classic fit, ankle length, straight leg, zip-leg and easy fit. And for men, they manufacture tapered leg as well as baggy, easy and loose fits.

A whole new vocabulary describes washes now found in jeans - mercerized, acid-washed, overdyed, bleached, rinsed, ring-spun, sandblasted, stone-washed, etc. Many of these washes are so subtle that they are not distinguishable to the layperson's eye.

Color has also affected denim in a big way. According to Jeanswear Communications, indigo blue will always be No. 1. But you'll find colors like brown, pumpkin, purple, gray and green. The trend seems to be to avoid lighter washes and go for the deep, overdyed colors like black and midnight blue. Natural and white continue their popularity.

Lee has tagged its finishes and colors with distinctive names like Pepper Used, Pepper Wash, Pepper Black, Midnite Ice, Black Ice and Double Black.

And mills are always experimenting with different fabric weaves and fiber combinations to make the fabric softer, more flexible and form-fitting.

"New jeans shouldn't feel like new jeans," says Juan Munoz, vice president of Wrangler Rugged Wear. "And this season, Wrangler offers outdoorsmen a wide selection of weathered denims."

Thanks to manufacturers like Cherokee, denim is becoming a staple with elementary schoolchildren. We're not just talking about denim pants, but dresses, skirts, jackets and outerwear. Polyfilled "frozen" denim coats look like jean jackets but perform like parkas. Also there are stadium, duffel, anorak and biker-inspired jackets - all with plenty of pockets, zippers and fancy stitching.

Lee Co. is enjoying brisk sales by manufacturing denim fashions for infants and toddlers. Pint-sized versions of adult styles are available, including the V-Yoke Jean and Snap Back Rider for girls and Chukker, Commando and Voyager for boys.

Companies who for years focused mainly on denim pants are now branching out and manufacturing other articles of clothing. For example, Guess? Inc. not only sells a skin-tight, three-zip jean (one zipper on the fly and one on each ankle), but everything from miniskirts to fragrances and eyewear. However, 80 percent of its annual sales of $400 million is from its denim collection.

Denim designers and manufacturers disagree with people who say that the popularity of jeans is fading fast. Jeans have been around for a long time, and the companies will continue to adapt to a changing marketplace to ensure success for years to come.