Today is Hallowe'en and in America that means only one thing to retailers: the climax of the autumn selling season. Since the Samhain Eve festival was brought to the New World by Irish immigrants in the 19th century, Hallowe'en has been thoroughly commercialised to the point where $1.5 billion (€1.66 billion) is splashed out annually on costumes, as adults and children dress up and act a little crazy.

Hallowe'en has in fact become the second-largest retail holiday after Christmas, and stores which sell masks and costumes - like the New Jersey-based chain of Party City shops - do 20 per cent of their business in October.

Men have shown a preference this year for dressing up as Elvis or Vice-President Dick Cheney (really scary), and women as Marie-Antoinette, a Playboy Bunny or a French maid. But unlike previous Hallowe'ens, there is less chance of being served by a skeleton or a ghost in city stores or at airline check-in desks.

Hallowe'en is more frightening this year in the wake of the September 11th attacks. People are not playing at being afraid, they are afraid, and are dealing with real fear rather than escapism.

The fun has gone out of flying, and definitely no monster masks will be allowed in airline terminals.

There has been a change too in what people will tolerate, and Hallowe'en mischief-making will not have the same edge. Trick-or- treating is banned from many shopping malls to avoid upsetting edgy shoppers.

Gruesome items like imitation severed limbs have been removed from the shelves of Party City stores. School children have been exhorted not to wear Osama bin Laden masks - that move might invite a beating-up.

The most popular costumes being bought this year are of America's new heroes - firemen and cops - according to Erik Mandell, Party City vice-president of marketing. And red, white and blue face paint has been selling out at Wal-Mart.

Sales of traditional witches' and wizards' costumes would in fact have been pretty depressed if it were not for a small boy called Harry Potter.

Wizard costumes have come into demand as excitement builds up, especially among pre-teens, for the release on November 16th of Warner's Harry Potter and the Sorcerer's Stone. Anyone on the streets of New York today can expect to encounter legions of kids wearing $75 kits comprising a cloak, a wand and a pair of Harry Potter's signature round-frame glasses.

The arrival of the movie could not be better timed for parents who are worried about their children's reaction to the awful events of September 11th and the arrival of chemical warfare. They can escape from the horror of falling buildings and anthrax into a world where pure good defeats faceless evil.

Kids do not have to worry that "He Who Must Not Be Named", the wicked wizard Lord Voldemort, really wants to harm their parents - unlike "The Evil One Who Hides" as President Bush calls Osama bin Laden.

The hype is already under way for the $109 million film version of the first of the Harry Potter books.

Mattel is selling a levitating game and a science set for potion-making, and Lego has produced a kit for building Hogwarts, the public school for wizards. Coca-Cola is spending $150 million on a TV ad campaign linked to the Potter movie debut and there will be a Time magazine cover and Harry Potter watches and trading cards from Hasbro's Wizards of the Coast unit.

But the marketing of the first, long-awaited Harry Potter movie is not as commercially crass as Hollywood would like it to be, thanks to the author of the Harry Potter books, J K Rowling. She insisted that there should be no images of the boy wizard on Coke cans.

Almost certainly at her behest, Warner rejected requests for promotional deals from Burger King, Kraft Foods and Baskin-Robbins which could have brought in millions of dollars. An exception was made for Hasbro which has been allowed to produce Bertie Bott's Every Flavour Beans - Harry's favourite.

J K Rowling is a strong advocate of literacy, and has ensured that Coca-Cola gives more than 1.5 million books to 10,000 libraries and donates 100,000 four-dollar coupons for children to buy books as part of the marketing deal.

The limit on Happy Meals hype could actually give the movie a more widespread appeal, as teenagers and adults would otherwise tend to see the movie as a "kiddy-flick".

There are a number of other movies which the Hollywood studios are releasing in time to inspire Hallowe'en costumes, including A Knight's Tale, The Musketeer and Lord of the Rings.

Disney is putting great store on its animated Monsters Inc, due out this weekend. Anything is better these days than the real thing.