The Fortean Times, the journal of the unexplained, holds its "unconvention" at the Commonwealth Institute in London and expects 14,000 people to come along over the two days.
The convention, dubbed Monsters, Madness and the Millennium, is believed to be the world's biggest gathering of experts in unexplained phenomena.
Experts say that, with only eight months to go before the millennium, reports of strange phenomena from around the world are on the increase.
The phrase pre millennial tension - or PMT - has been coined to describe the stress many people are experiencing in the run up to the year 2000.
Many normally rational people are convinced the world will come to an end on the millennium.
A member of one of these apocalypse cults is Carlos Roa, the Argentinian national side's goalkeeper, who has refused to discuss a new contract with his team, Real Mallorca, because he says the world is coming to an end.
Daniel Wojcik, an associate professor of folklore at the University of Oregon, is one of the speakers at the convention.
Mr. Wojcik, who has written a book The End of The World As We Know It, says mankind has always been fascinated with worldly destruction and odd phenomena.
He told BBC News Online: "The approach of a new millennium has increased the number of people who believe in a coming apocalypse."
'Apocalyptic fears are widespread'
Mr. Wojcik says opinion polls in the United States suggest somewhere between 20 and 40% of the population believe Armageddon is imminent.
He says: "There is nothing in the Bible about the world ending in the year 2000 but these ideas have grown up as a sort of folk belief."
Mr. Wojcik says there is an interesting dichotomy in that many millennialists blamed technology and industrial progress but promulgated their ideas through the Internet.
He says: "Millennialists are not all the same. There are many different strands of belief.
"Some are very passive and are simply waiting for the return of the Messiah while others are more aggressive militia groups who feel they have to do something to bring about Armageddon."
Mass suicides could rise
He says cults such as the Branch Davidians and Heaven's Gate may have been influenced by millennialist ideas.
But he says: "The millennium is not going to be as violent as some people think, with mass suicides and such like. But we can expect to see this sort of stuff on the increase."
Other speakers include Damian Thompson, who will explain the significance of the millennium and Tony Healy, who has spent years searching for Australia's answer to the Yeti, the Yowie.
Emmett Sweeney, a self-styled alternative Egyptologist, will give an intriguing talk entitled Escape from Armageddon: The True Secret of the Pyramids.
Sunday's speakers include Jan Bondeson, an experts on mythical creatures such as basilisks and mermaids and Sergio della Sala, who will explain the "myths of the mind".