There are 3,000 tickets still available - the first time in a decade that the event has failed to sell out.
Slow sales have been blamed on a combination of bad weather last year and the controversial choice of US rapper Jay-Z as the headline act. His inclusion is said to have put off many traditional festivalgoers, who claim that his music style does not fit in with Glastonbury.
In 2007, 140,000 tickets were bought in just two hours. However, this year is a different story with only 100,000 tickets selling on the first day and organisers struggling to shift the remaining 35,000 for a line-up which includes The Fratellis, Kate Nash, James Blunt and The Feeling. Amy Winehouse is booked to appear on Saturday but her performance is in doubt after she was admitted to hospital suffering from the early stages of emphysema.
Despite the sales lull, a spokesman for the festival, held at Worthy Farm in Pilton, Somerset, claims that there are no fears the rest of the tickets will be snapped up.
Chrispin Aubrey said: "From information we have gained, the main reason tickets haven't sold as fast is the result of last year's weather. It rained continuously in 2007 and this made it very difficult for those attending.
"We still expect this year to be a sell-out and believe that the few thousand tickets left will be snapped up before the main acts start on Friday."
In 2005, the festival was plagued with storms and flash flooding. In 2006, there was more rain - resulting in a mud bath - and 2007 saw it rain relentlessly throughout.
People may also be wary of the nightmarish journey that can involve traffic queues of up to eight hours long as local roads are swarmed by 50,000 vehicles.
Glastonbury organisers have tried to make many changes to the festival, including improvements to drainage (costing around £100,000), camping (40 acres have been freed up for more space) and the establishment of three dedicated medical centres for festivalgoers, which will be open 24 hours a day.
Also this year, there will be 3,000 toilets and 10,000 waste bins on site, aimed at creating a more pleasant and hygienic environment for everyone.
Crime has fallen 90% between 2000 and 2005, according to Avon and Somerset Constabulary. Superintendent Adrian Coombs of Avon and Somerset Police said: "onsidering the size of the festival, it is a very safe place and crime has decreased by a huge amount."
As for weather conditions, there is a small glimmer of hope for the festival, as weather forecasters are predicting good weather for the first time in five years. According to the Met Office, it will be sunny and dry, with temperatures reaching around 20 degrees. Light showers are predicted for Saturday morning but should clear quickly.
But some festivalgoers are taking no chances.
A group of druids, led by Archdruid King Arthur Pendragon, took part in a "sun dance" in London's Hyde Park, saying a prayer for sunshine.
Let's hope it helps because as Conor McNicholas, editor of the music magazine NME, says: "Glastonbury is the mother of all festivals but it can be a real mother if it rains all weekend."