Dave Surgan dropped into a crouch, then leaped into the air and let out an eardrum-rupturing yelp.

His imitation of a crazed monkey during a recent audition at Universal Orlando helped him land a job frightening some of the hundreds of thousands of visitors who will come to be scared at the theme park resort's Halloween celebration.

"Once, they had to call the paramedics because a girl started hyperventilating," said Surgan, who in past years played a crazed chain-saw operator and a mutated dinosaur.

Not so long ago, Halloween was merely a one-day holiday, observed primarily by neighborhood kids dressed in fake blood, plastic teeth or superhero costumes.

Not anymore. Over the past five years or so, the nation's $11 billion amusement park industry has appropriated the holiday as its own, helping transform Halloween into a month-long celebration.

"If there are still theme parks out there that aren't celebrating it, they need to get their heads examined," said James Zoltak, editor of Amusement Business, a trade publication. "It's a moneymaker, almost universally."

Although the International Association of Amusement Parks and Attractions keeps no figures, industry experts estimate that millions of people go to Halloween celebrations at parks around the nation, generating tens of millions of dollars.

For Terri Lacroix, the appeal of the Halloween celebrations comes from the adrenaline rush she gets anticipating where the next grotesquely masked figure is going to jump out at her in the confined space of a haunted house.

"I don't like roller coaster rides, but I love scary movies. This is my adrenaline rush," said Lacroix, an Orlando catering manager, as she left the "Skool" haunted house at Universal's Halloween Horror Nights.

Nationwide, Halloween has grown considerably as a holiday, and this year consumers are expected to generate $3.3 billion in Halloween spending, according to the National Retail Federation. Celebrations have spread abroad to amusement parks in places such as Mexico and Brazil that do not have strong Halloween traditions.

"One of the things we know is that this is a worldwide trend. It's not just in the United States," said Beth Robertson, a spokeswoman for the amusement park association.

The parks' embrace of Halloween has been for economic reasons as much as creative ones. Before Southern California's Knott's Berry Farm became the first park with a major Halloween celebration 33 years ago, most regional theme parks closed soon after Labor Day.

Halloween gave the regional parks incentive to extend the season and offered year-round destination parks in Orlando and Los Angeles a marketing tool to get people through their gates during what was traditionally a slow period.

"People just love to be immersed in a frightening Halloween experience. They love giving up that control," said Jim Timon, senior vice president of entertainment at Universal Orlando, who helps plan the park's Halloween Horror Nights.

Knott's Berry Farm began its Halloween celebration in 1973 with some scary decorations and a few dozen "monsters" lurking in the fog to jump out at unsuspecting guests. This year, the celebration will feature 12 mazes, five "scare zones," six live shows and more than 1,000 "monsters" roaming the property. The Halloween celebration accounts for about 15 percent of the park's annual business, attracting 500,000 people from as far away as Germany.

Busch Gardens Williamsburg in Virginia started its Howl-O-Scream celebration in 1999 with two attractions and three shows that operated over three weekends in October. This year, the Halloween celebration started in mid-September with five haunted houses, four "scare zones," five attractions and eight shows. It also accounts for 15 percent of the park's annual attendance.

The parks vary in scare intensity from the child-friendly mellowness of trick-or-treating with Disney characters at Walt Disney World to the more R-rated anxieties generated by the "Slash" show at Worlds of Fun in Kansas City, which is geared toward teenagers and young adults.

" 'Slash' is kind of edgier, a magic show with a lot of gore and blood, people cut in half," said Nick Guevel, a spokesmen for Worlds of Fun, which started developing a scary Halloween celebration three years ago.

Creatively, theme and amusement parks are well-positioned to handle the special effects that celebrants have come to expect from Halloween. Some park officials, such as Universal's Timon, spend 11 months planning the Halloween celebrations.

"For theme parks to become involved in Halloween, it's kind of a natural fit because it's something that is so easily translated into a live experience," Timon said. "We're able to take what you expect the Halloween experience to be and blow it up a thousand times."

This year, the nation's theme and amusement parks are counting on successful Halloween celebrations more than ever. A season of great promise in the spring gave way to what is expected to be flat attendance for the year because of recent hurricanes and high gas prices.

"Everybody is really gearing up for it," said Dennis Speigel, president of International Theme Park Services Inc., a consulting firm. "The parks are putting a heavy emphasis on it, so they can help generate the numbers that will help pick up some of the drop they've seen in late August and early September."

An actor, center, is sacrificed in a "bloodletting" ceremony at Universal Orlando's Halloween Horror Nights, which attract hundreds of thousands of patrons,Nona Lee Davis performs in her role as the Terra Queen at Universal Orlando's Halloween Horror Nights. Many amusement parks offer extended Halloween festivities at what used to be a slow time for business.James Keaton has makeup applied for his role as Eel Mouth at Halloween Horror Nights.