In the stillness of a moonlit night, you're by yourself, lost in the woods, and you're frightened.

Up ahead -- a graveyard, and -- what's that? Funeral music! These are the spooky sounds heard in many theatrical "haunted houses" and in horror movies which are popular in the United States around Halloween.

Halloween is one of the world's oldest festive occasions, celebrated in the United States on October 31st, the evening before the Christian holiday of All Saint's Day, or All Hallows Eve. The age-old celebration still reflects our fears - and stirs some social and religious controversy, as well.

Experts trace Halloween, essentially a costumed parody of horror and fright, to the ancient pagan wintertime festival of the Celts known as Samhain many centuries ago. Co-opted by the Catholic Church before the Middle Ages, the celebration was renamed "Halloween," Hallow's eve, the day before a holy day that honors Christian saints.

Halloween expert Nicholas Rogers says the celebration combined pagan and religious elements. "It's really a mix of probably Celtic pagan belief and Christian belief and then associated with, as the name suggests, the 'Eve of All Hallows,' which is the eve of 'All Saints [Day.]' So Halloween is really the modernized version of the eve of All Saints. And All Saints [Day, Nov. 1st] and All Soul's Day [a day later, Nov. 2nd] were Christian holidays commemorating the dead. We've made it a secular holiday. It's no longer a religious holiday. [But] it still carries, I suppose, some of the supernatural mystique of the old holiday, when people believed in magic, witches, and witchcraft."

Mr. Rogers, author of the book, "Halloween: From Pagan Ritual to Party Night," says that until more recently in the United States, Halloween had generally been a lighthearted event -- a night of fun for children to get dressed up and pretend. "I think in the 1950's, there was an attempt to try and sort of infantilize the holiday - to emphasize it as a sort of a 'kiddies' night,' and that was the origin of what we call 'trick or treating,' that began in earnest in the 1950's, particularly in the North American suburbs."

Trick or treating is the child's ritual of putting on a costume and visiting homes in the neighborhood for gifts of candy. The phrase "trick or treat" implies the child threatens a prank if he or she doesn't receive a treat of candy. Each year, there are always some children, especially teenagers, who take part in "tricks" -- sometimes serious pranks like vandalizing property. But trick or treating - like Halloween itself -- was and generally remains a parody of doing evil.

"People who celebrate this, for the most part, don't take it seriously, " says Richard Lachmann, a professor of sociology at the University of Albany in New York. "They don't believe in the occult. They don't believe in witches. They're just partying and wearing costumes appropriate for that day. There are some people with various religious views, who do take it seriously and are upset by it, but they're giving it seriousness that people who actually celebrate don't share."

In recent years, however, many Christian conservatives have condemned Halloween as a celebration of evil and paganism. Richard Lachmann says they miss the point. "I think it's a part of a larger view that they're worried that they live in a decadent society, where children aren't presented with clear moral values, and so they're [children are] going to be open to bad influences -- and parents worry that they're going to have a hard time counteracting that. Generally, it's easier to express these sorts of worries by focusing on a particular sort of image. So when you see something that looks very different from what you're used to and kids focus on that, I think that can become very scary for some parents."

But the sociologist says that many parents are rightly concerned that Halloween -- especially as portrayed in contemporary films -- relaxes the taboo against promiscuous sex and violence. He suggests parents can use the occasion to bring up the matter of values with their children. "Among parents, this is part of a larger debate about what do we let our kids do, what lines do we draw?" he explains. "What's worth potentially getting into an argument with kids and saying, 'This, we won't allow.' In my view, kids dressing up as witches and having fun... that's something I wouldn't argue with my kid about. Other parents may feel it's a first step along the path going in a bad place. So that's something worth making a fuss over."

There's strong cultural pressure to celebrate Halloween, says author Nicholas Rogers. "Bars, restaurants, costume makers, the candy manufacturers -- they're the people who gain most out of this." He points out that there's a lot more pressure to buy Halloween products these days. "No sooner do the back-to-school products disappear from the supermarkets than the Halloween products come on. I open my e-mail and I get 'E-bay' invitations to buy costumes and so on. So I think there's a lot of commercial pressure to spend money."

Indeed, Americans spend a total of about seven billion dollars a year on Halloween products. Only at Christmas do they spend more. Some Halloween experts say this kind of out-of-control spending may be the most frightening part of all.