Only true-blue denim aficionados know the significance of May 20, 1873: the birthday of jeans.

That was the day dry-goods purveyor Levi Strauss and tailor David Jacobs -- both drawn to the western U.S. by the gold rush -- patented the small metal rivets found on the pockets of jeans.

These sturdy pants remained primarily for laborers until celebrities such as James Dean and Elvis Presley popularized them in the 1950s. From that point forward, jeans were ensconced in popular culture and fashion.

In the early 1990s, however, denim moved in a new direction.

That is when Japanese tailor Hidehiko Yamane began producing jeans on vintage shuttle looms and hand-painting his trademark seagull logo on the back pockets.

He made just 14 pairs a day and named the jeans for Evisu , the Japanese Buddhist folk god of money. The completed pants retailed for about $400 a pair and quickly became a cult hit in Japan.

In 1994, Yamane teamed up with distributor Peter Caplowe, increased production and marketed the jeans internationally.

But Yamane stayed true to his vintage methods of dying and making denim; today he claims to be the inspiration for 7 For All Mankind and True Religion ( TRLG), the first American brands of premium denim.

A Cut Above

But why spend up to $800 on pants you can easily find for $45?

I used to wear each pair of my stiff Levi's 501 jeans for months until they were butter-soft.

Then they would rip, I'd buy a new pair and began the long process of breaking in my jeans once more.

I'd heard of celebrities spending several hundreds of dollars on jeans. But I didn't understand why until I took a few pairs into a Saks ( SKS) dressing room.

These jeans were soft. They felt as comfortable as pajamas. And I understood why movie stars always looked so good in them. The reflection of my derriere in the Citizens of Humanity pale-blue denim astonished me. I had no idea pants could be so flattering.

Shopping for premium denim can at times be overwhelming: High-end department stores' denim boutiques are veritable seas of indigo fabric.

It helps to know that each designer boasts infinitely different styles and "washes," which refers to the dye process of denim.

True Religion "Jennifer" ($240)

For instance, 7's jeans often have a trademark fade at the front of the calves and the back of the upper thighs; other styles, such as Rock and Republic men's line, are imbedded with tiny vertical stripes (called "whiskers").

What wash you prefer is simply a matter of taste. However, I did notice that with the exception of 7's, darker washes tend to be stiffer than lighter ones. While those shiny, deep finishes such as Levi's Capital E's Skimmer ($158) lend a more elegant, dressed-up look to jeans, it is often at the price of comfort.

The feel, fit and look of premium denim is achieved with a blend of domestic and imported fabric, often from Italy or Japan. And tailoring the final product is often an involved process. President and creator of Lyric Jeans ( LYJN) Hanna Rochelle Schmieder told me that each time the wash of the fabric was adjusted, the jeans had to be retailored.

To perfect her company's offerings, Schmieder took sample pairs -- and some friends -- into department stores to try them on in the typical fluorescent-lighted setting.

"I wanted to make sure that ours fit the best," she explains. Unlike many other male-run jeans companies, Schmieder has the advantage of being able to test everything in the Lyric line. (The jeans are available only for women now; the men's line will debut next year.)

The premium denim market is fiercely competitive. Upstarts like Lyric must battle with each other, as well as with the lines of established names like Levi's.

Getting a Leg Up

Additionally, denim companies must compete with the jeans available from haute couture design houses like Prada and Karl Lagerfeld.

Rock and Republic CEO and head designer Michael Ball (whose company started from a single pair of jeans he made for his girlfriend in 2002) boasts: "We plan to expand and eventually dominate globally."

Rock and Republic's collection can be purchased at many of the major department stores as well as through online boutiques.

Schmieder believes her newly launched Lyric jeans have their own edge.

She bought the rights to a number of songs such as Revolution by the Beatles and Love Child by The Supremes. These song lyrics will be written on the jeans (or just on the insides, for a toned-down version), and each lyric design will reflect the unique aspects of the songs.

The jeans will be on sale in select stores in spring 2007; basic jeans without lyrics will debut on the Lyric Web site before the end of the year.

Schmieder also designed the back pockets of her jeans to be extremely flattering, even compared with the other high-end brands. "I own about 20 pairs of designer jeans, and now I only wear Lyrics," she says. Her company went public this past February, and Lyrics will sell for between $185-$800 a pair.

Other original approaches to premium denim include Levi's new Eco line. Made from organic cotton, with premium denim cuts and attention to detail, Eco's -- like Lyric's -- are a new twist on a old favorite.

The Perfect Pair

Women's designer jeans are sold by waist sizes in inches, like men's pants, rather than the traditional sizes.

While this tends to make sizes more consistent across brands, the buyer will notice one other important difference: Unlike mass-market brands, most women's premium denim has a very low waistline.

Rock and Republic
"Roth Urban" ($266)

The height of jeans relative to your waist is referred to as the "rise"; high-end jeans' average rise is often only 7 or 8 inches, whereas the rise for cheaper brands is usually around 10 to 12 inches. While premium denim compensates for this low rise by tailoring jeans higher in the back, the potential for wardrobe malfunctions can be high.

To compensate, you can buy designer denim a size up and wear a belt, or try the men's styles. (Unlike Evisu, which debuted with men's styles, most American denim premieres with women's lines and later adds the men's.)

Though they may hang a little looser, the men's styles have a higher rise and still look fantastic. I found the men's Rock and Republic jeans with variegated color whiskers both flattering and comfortable.

No matter what the brand or style, be assured that premium denim is well worth the price tag.

The feel and look of designer jeans is addictive: Once you've graced your hips with high-end jeans, it will be impossible to go back.

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Penelope Dane is a writer and sociologist living in Baton Rouge, La. She is currently working on her M.F.A. in fiction and conducting research on teen poetry.