IT IS often dismissed as a commercial American occasion but there is no doubt that Halloween is growing in popularity in Australia.

More than 4 million people - or 20 per cent of the population - will celebrate Halloween this year according to a survey by McCrindle Research.

It's a scream... Juliet and Dan Toomey with Ashley, 10, and Lola, 5, in Paddington. Credit:Adam Hollingworth

Social analyst David Chalke says this is probably due to the growing commercialisation of the event - he likens it to Valentine's Day - and the fact that most people who take part see it as simply a good excuse to have a party.

Halloween has proved a treat for retailers with demand for pumpkins, spooky costumes and accessories increasing. Pumpkin sales are up 50 per cent on last year as farmers and supermarkets cashed in on the Halloween trend. By Friday, Woolworths had sold more than 11,000 pumpkins and expected the number to double during the weekend.