Sometimes something is so ugly it's cute.

That's the closest thing to an explanation you'll get from troll collectors.

Those thirtyish and older probably remember trolls, the wrinkle-faced, fluorescent-Albert-Einstein-haired, elfin dolls with the large eyes.

In the '50s, Helena and Martii Kuuskoski of Finland transformed some clown dolls into trolls and sold 150,000 of them worldwide by 1959.

But the dolls that most collectors prize were made in the early to mid-1960s based on a wood carving Thomas Dam of Denmark did for his daughter. The Dam doll trolls were produced in a Florida plant, and American kids were encouraged to adopt them.

As with any hot toy, there were imitators. A handful of companies -- Uneeda Wishniks, Scandia House, Russ Berrie, Kamar, Knickerbocker and Allied Toys -- hit the market, each changing the design slightly.

By the early 1970s the troll craze had cooled, and Dam withdrew his trolls from the U.S. market, continuing to sell in Scandinavia.

They made their comeback in 1982 when Eva and Steven Stark formed the EFS Marketing Association in Farmingdale, N.Y., and arranged with Dam to import his original molded designs. They called the new product Norfin. Russ Berrie of Oakland, N.J., reissued his trolls in 1983, and adult collectors began buying them again for their children and grandchildren and for themselves.

"If you love them, you love them," says Diane Scalia, a legal secretary in Feeding Hills, Mass., who owns 200 trolls. "Only a true collector can understand that and not say, 'Wow, what a weirdo.' "

Those who monitor trends in toy sales are just beginning to see the troll invasion.

"I just heard about this," Bob Seligman, editor of Toy and Hobby World in New York City, said. "I just spoke to a retailer in California who says trolls are hot."

Nanette Comstock, who runs Toys Etc. in San Anselmo, Calif., with her husband, Dennis, says that "trolls have been a great seller since late last year."

The Norfin dolls and the original Dam dolls have different facial expressions for different dolls. The Russ Berrie versions keep the same expression.

But some swear by Russ Berrie, while others are true to Norfins. Still others will collect anything that's old.

"I have about 2,500 trolls," says Lisa Kerner, 29, of Whitman, Mass., who puts out Troll Monthly Magazine.

About five years ago she put a notice in Doll Collectors United magazine asking for other troll collectors to contact her.

"I got so much mail that I started the newsletter," she says. Her 63 subscribers run carefully hand-lettered ads asking for a rare mermaid troll or offering to sell a set of six Lingonberry Trolls "firm, $150, will not split up."

For $18 a year you get the newsletter, a certificate, a troll button and key chain. (For information, write to Troll Monthly, 55 Plymouth St., Whitman, Mass. 02382.)

The Norfin "Adopt a Troll" fan club has about 4,000 members.

Jodi Levin, with the Toy Manufacturers of America in New York City, says, "I'm beginning to hear about them, but they are not huge yet."

New troll dolls sell for as little as $2.19 for the tiny ones to as much as $85 for 18-inch ones with 100 percent wool hair. Old trolls can sell for 10 cents to $200, depending on the luck of the buyer and the rarity of the model.