ORLANDO, Fla. - Universal Orlando's first foray into Halloween Horror Nights 21 years ago involved one weekend, a single haunted house tucked away in the back of the park by the "Jaws" ride and some people in store-bought masks jumping out of dark corners.

What was largely an experiment that first year has evolved into a monster draw for the Orlando theme park. Once the creative types figured out that people loved having the wits scared out of them and would pay for the privilege, the challenge was on to create something bigger and better every year. This time the event runs 25 nights in September and October and takes over the entire park, with eight themed haunted houses and mazes, two live shows, sophisticated makeup, film-quality set decor, gallons of fake blood and as many as 1,000 "scare-acters" involved. Planning and production takes place year-round now, and the event draws hundreds of thousands of people who pay $42 or more to attend.

"I think it all has to with escape," says Patrick Braillard, a production show director and one of the gleefully demented minds behind the event. "People love to be transported, they love to be taken somewhere they're not familiar with. So our job is to create eight immersive environments. When they walk in, they are completely somewhere else."

The concept is basically the same as in the cheesy neighborhood haunted houses that spring up every year to raise money for charity: costumed characters jumping out of dark, creepy surroundings to make unsuspecting patrons scream. But for a generation raised on computerized special-effects, slasher movies, video games and the Internet, Universal and other theme parks that get into the scare business every October have had to step up their game. And that means realism.

The Universal haunted houses and mazes are on sophisticated studio soundstages and all have a theme and eerie story attached. Attention to detail and sense of place is stunning. In one, visitors walk through a misty haunted cemetery as corpses emerge from disturbed graves and crypts. In another, souls that perished at sea on Christopher Columbus' fourth ship forever haunt a Spanish fort. (The gallows setting in that one alone could induce nightmares for those who are prone.) Another has an obligatory tie-in to a Universal movie, in this case "The Thing," which comes out in mid-October. A Lady Luck gambling theme - it's the 21st year for the event, get it? - is a common thread throughout.

Horrible-looking zombies and other ghouls lurk in "scare zones" throughout the park. This is definitely not for younger kids and the faint of heart.

"You've got moments of breathing room, like the bathrooms and any food lines that you might go into, but pretty much you're ours as soon as you hit the gate," Braillard says.

A note to Harry Potter fans: Universal Orlando consists of two parks. Halloween Horror Nights takes place at Universal Studios Florida, not at its sister park, Islands of Adventure, where The Wizarding World of Harry Potter is located.

Universal Studios Hollywood stages its own Halloween Horror Nights, with original mazes based on '70s shock rocker Alice Cooper's "Welcome to My Nightmare" theme, Rob Zombie's "House of 1000 Corpses" and "The Wolfman." Also new this year is a maze built around "La Llorona," the fearful story of melancholy and murder that has terrified Mexican and Latin American children for generations. For the uninitiated, La Llorona was doomed to wander the earth forever after drowning her children in a desperate attempt to win a lost love.

At Busch Gardens in Tampa, the annual Howl-O-Scream event will feature "The Dark Side of the Gardens" for 17 nights, with seven haunted houses and mazes, plus the streets will be crawling with hideous zombies. Creative director Scott Swenson says twice as many actors are hired just to haunt the streets inside the park now than were involved in the entire event when it started 12 years ago. That first year, there were three haunted houses, a few costumed monsters roaming around and a couple shows. Now Busch Gardens hires an extra 1,000 people and artists spend hours creating detailed silicone prosthetics and masks for the characters.

Swenson says he thinks people come to the park to be scared for the same thrill they might get from extreme sports.

"It's an adrenaline rush that if you let your imagination go is just as real as being terrified anywhere else," he says. "But deep inside, you know you're still going to be safe. You can get close to the edge."

For families that want some Halloween fun that doesn't involve uncomfortable surroundings, gore and body parts, Walt Disney World has Mickey's Not-So-Scary-Halloween Party. The costumed little ones can collect trick-or-treat candy from throughout the Magic Kingdom and see the Boo-To-You parade that includes stars of the famous Haunted Mansion attraction. Disney caps it off with a Happy HalloWishes fireworks show.

The SeaWorld parks in Orlando, San Antonio and San Diego also are offering family friendly Halloween events with undersea themes. Kids can trick-or-treat throughout the parks and check out the themed shows, including Sesame Street's "Countdown to Halloween Show."