Size does matter.

People won't be heading to their neighborhood theater to see the new movie based on Stephen King's best-selling novella "The Sun Dog." Nor will they go there for the debut of Walt Disney Co.'s much anticipated "Fantasia 2000" next year.

They'll have to trundle to the closest Imax theater.

The days when large-format films offered little more than documentaries about nature and were screened only at science centers arid theme parks have come to an end. As this specialized niche of the entertainment industry approaches its 30th anniversary, it has started to explode.

"What's happening today with the large-format film industry reminds me in many ways of the advent of sound," said Bob Rogers, founder of BRC Imagination Arts in Burbank and a 20-year veteran of large-format filmmaking. "Some director in 1927 asked why would anyone want to hear an actor talk? Every once in a while, a new opportunity opens up and catches the industry by surprise."

More than 100 new large-format theaters are slated to be built worldwide before the end of 2000, bringing the total to 364, according to trade publication MaxImage.

The vast majority of those theaters - which immerse viewers in extra-wide screens with greatly detailed visual images - will be built as part of commercial venues rather than at museums or theme parks.

At the same time, the number of movies being made to play on those screens is going up - about 24 new films to be released in 2000, double the number coming out this year.

"With in-home entertainment options such as the Internet and DVD players growing tremendously, the reciprocal demand for better, more unusual, more awesome out-of-home entertainment surges," said Bradley Wechsler, chairman and co-chief executive of Imax Corp., which makes films and the hardware to screen them. "And that's exactly what large-format theaters like Imax provide."

So far, large-format films have failed to attract large audiences, mostly because they run less than an hour in length (in part due to the constraints of making the movies, which cost anywhere from $2 million to $12 million to produce).

That led filmmakers to crank out a steady stream of documentaries on everything from outer space to the African veldt - the ideal fare for museums but not necessarily big crowd-pleasers.

But more traditional storytelling is in the works.

Laguna Beach-based MacGillivray Freeman Films' "Everest" and "Encounter in the Third Dimension" by nWave Pictures in Sherman Oaks have been hugely successful. "Everest," which documents a 1996 climb to the mountain peak mere days after a vicious storm killed members of another expedition, grossed more than $100 million. Moreover, the film broke into the domestic top 10 box-office rankings, suggesting that a large percentage of its audience was comprised of first-time large-format moviegoers.

To find real success, the industry has to convince the public to think of large-format films as entertainment rather than education. That's where the big names come in.

Steven King's Imax film is expected to bring many of his fans into Imax theaters for the first time, as are upcoming films on the Las Vegas animal-training duo Siegfreid and Roy.

Even more is expected of"Fantasia 2000." Disney and Imax brokered a deal in which the movie will screen exclusively in the large-format theaters for its First four months of release, before moving to mainstream theaters. "If Fantasia is successful, it will be heavily emulated," Rogers said.

Moreover, the large movie format would seem uniquely fitting for such digital effects-driven blockbusters as "Titanic" and "Twister." There have even been persistent rumors that the next "Star Trek" movie will be made in the large format.

Not everyone is convinced that oversized dramas are the industry's future. The majority of large-format theaters can still be found in science centers, generating about 70 percent of the industry's total box-office receipts.

"The main appeal of the genre is the ability to take people to a place they've never actually been," said Alec Lorimore, vice president of production and development at Macgillivray Freedman. "We're always looking for bigger adventures, but I don't think you'll ever see a romantic comedy in a (large-format theater), since that's not what the technology is suited for."

Finances are the biggest factor holding back the industry. The limited number of large-format theaters, coupled with slim profit margins on the movies, is not yet strong enough to entice critical financial backing.

"I spend all day, every day, on the phone with the finance people," said Charlotte Huggins, president of nWave Pictures. "They're all interested, but now we need to close the deals and get the money in the bank. I'm confident it will get easier, but it's killing me."

Large-format cinema is growing at a faster rate than any other niche of the film industry. Of the more than 100 new large-format theaters currently slated for construction, many are being installed in standard multiplex theaters.

Los Angeles is poised to become one of the world's leading cities in terms of large-format theaters. In addition to the two currently operating at Ontario Mills and the one at the California Science Center, others will open next year at Universal CityWalk and the Howard Hughes Center.

The more theaters that open, some believe, the greater the demand for more films to play there. But until more film titles exist, there is little motivation to build new theaters.

"Right now, the industry is overcoming the product versus pipeline problem, which is in part responsible for the its sudden budding," said Kevin Skislock, an analyst with Irvine-based Laguna Research Partners. "As each hurdle is overcome, the industry will grow in spurts."