Individuals and big corporations are hosting holiday events dedicated to "ugly" or "tacky" Christmas sweaters. Fashionable retailers like Bloomingdale's, H&M and Abercrombie & Fitch are putting snowflake and reindeer styles in windows and catalogs. Meanwhile, thrift stores and websites are out of stock of vintage designs, the more elaborate the better.

Brian Philippoi, a 26-year-old employee of a Web design firm, wore a bulky cream sweater with a bright alpine print along with dark skinny jeans and sneakers to a recent party. He describes the sweater as "very 1960s Swiss ski resort." "It's like walking a Great Dane," he says. "You have to show it who's boss."

Searches for "ugly Christmas sweaters" are up 30% in December compared with December last year. On eBay this year, someone paid $282.59 for a sweater with three reindeer across the front, an increase from the website's most expensive holiday sweater last year, which sold for $200. Ebay's sales of holiday sweaters are 24% ahead of last year.

Dunkin' Donuts is giving $60 gift cards to people who post pictures of themselves on Twitter by Dec. 22 in holiday sweaters that are "kitschy or cute or glamorous or ho ho horrible," says a company spokeswoman.

The Christmas sweater started out as homemade, became a mass-market hit in the 1980s and has been a dependable seller ever since, even though "fashion snobs look down their noses at them," says David Wolfe, creative director at the Doneger Group consulting firm. For many, they bring back memories of grandma and a time of year when "everybody just drops their sophistication and goes for the heart."

Randall Ferguson, a 27-year-old who grew up in Michigan, began hosting "ugly sweater parties" in college. "It started out as a way for us to mock our moms," he says. For a party he hosted last week in his Manhattan apartment, Mr. Ferguson wore a snowman sweater that he bought for $10 earlier this season on eBay.