The New Wrinkle in Men’s Trousers : Innovation: They’re promised to be smooth no matter what, and they’re <i> cotton</i> . We tried them at home. The results? Well, don’t lose that iron.

Maybe you’ve seen the TV commercial. Daredevil Dave Osborne, dressed in a denim jacket and Haggar slacks, is strapped, standing up, to a car chassis. Seconds later, the vehicle barrels through a carwash and crashes into a wall. Through a cloud of smoke, Osborne announces that his pants are “still not wrinkled.”

Haggar hopes consumers get the message that its new pants stay smooth--no matter what. Ditto for Lee, Haggar, Levi’s, Louis Raphael, Thomson and half a dozen other makers of wrinkle-less pants.

Why all the waxing on wrinkles? Because this new generation of pants for men and boys is cotton.

“Any time a claim is made that a product will come out of the washing machine and hold its crease and stay flat, the first thing the customer thinks of is permanent-press polyester,” says Ritchie Russell, senior product manager for Lee.

The terminology used to identify these products--wrinkle-free, wrinkle-resistant, no-wrinkle-- may also be confusing and misleading, notes Frank Bracken, executive vice president at Haggar. That’s why Haggar hang tags clearly state that the pants are wrinkle- resistant “out of the dryer.” After a day’s wear, Bracken says, any pants will develop some wrinkles.

Not all wrinkle-resistant slacks are created equal, says Richard Allender, chief executive at Farah. The difference lies in the varying methods manufacturers use to apply the key ingredient--a protective resin--and then cure it, or melt it into the fabric. The process is not described on the labels but the result may determine how long pants resist wrinkles.

In a week’s worth of home testing, following label care instructions, this is how the three major brands of treated cotton pants performed:

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Brand: Savane by Farah “no wrinkles” loose-fit, pleated twill slacks; $36-$45

Performance: Moderately pliable finish; softened considerably after one washing. Virtually unwrinkled out of the dryer but soft, noticeable wrinkles at the crotch after a day’s wear.

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Brand: Lee “wrinkle resistant” preshrunk plain-front cotton trousers; $32-$38

Performance: Slick, stiff finish; stiffness softened after three washings, and only a faint line remained where there once was a noticeable crease. Obvious wrinkles at the crotch, seat and back of knee after a day’s wear.

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Brand: Haggar “wrinkle-free” pleated cotton twill slacks; $38-$45

Performance: Shiny and board-like; sheen subsided after three washings; stiffness lingered until the fifth wash. Virtually wrinkle-less out of the dryer. Mildly wrinkled around crotch and back of the knees after a day’s wear. Crease barely recognizable after fifth wash.