SUV and pickup truck owners — already stung by rising gasoline prices — are paying another penalty when it comes time to trade in or sell: falling resale values for the gas-thirsty vehicles.

The resale value of large SUVs and pickup trucks is slumping in response to a supply glut, lower demand, higher gasoline prices and lower sales of new SUVs and pickup trucks, analysts say.

Automakers now have to boost discounts on new SUVs, hurting prices for new and used models.

According to www.edmunds.com, an online shopping guide, trade-in values on trucks and SUVs have dipped while dealers are offering larger incentives to people trading in compact cars. The average trade-in value of a year-old SUV, for example, is $24,374, down about 5 percent from a May 2004 average of $25,651. Trade-ins for 3-year-old SUVs have waned nearly 8 percent, from $18,097 in May 2004 to $17,573 today.

Roy Holderbaum's love affair with his 1993 GMC Yukon recently came to an abrupt end when his gas bill shot to $100 a week. Now, he wants someone to take the hulking SUV off his hands.

"It's a gas-guzzler. I'm selling because I can't afford to drive it back and forth to work," said Holderbaum, 23, who has a 20-mile commute.

But many owners of large SUVs are finding it harder to unload their rides with gas prices above $2 per gallon, a glut of used SUVs on the market, and consumer tastes shifting toward smaller, more fuel-efficient models.

"If the rebate on a Chevy Suburban goes up $1,000 this month, usually the Suburbans sitting out there in our auction lane all of sudden lost, maybe, $500 worth of value," said Tom Kontos, chief economist at ADESA Inc., a Carmel, Ind.-based firm that tracks wholesale prices of used vehicles.

The drop in trade-in values for large SUVs is another indication that they are losing their appeal with American consumers.

The big trucks that were the family vehicle of choice and a major source of profits for Detroit automakers during the 1990s still account for more than 1 million annual sales. But the segment has taken a hit since 2004 with competition from car-based SUVs with better gas mileage.

While no one is ready to pronounce the death of the Chevy Tahoe or Toyota Sequoia, consumers trying to sell large SUVs are seeing firsthand that Americans are not as interested as they once were in the big family haulers.

"I thought for sure I'd sell (mine) right away," said Holderbaum, who has spent about $10,000 over four years to upgrade his Yukon. "But nobody wants to pay for that kind of gas."

Rising gas prices may help explain a recent glut in large SUVs for sale by private owners.

Autotrader.com, an online vehicle seller based in Atlanta, has more than 100,000 more SUVs listed in online classified ads today than a year ago, according to spokeswoman Louise Barr.