The first Amsterdam Dance Event, held from Thursday 17 to Saturday 19 October 1996, drew just 300 professionals, who met at De Balie by day and went clubbing at night.
ADE now draws around 600,000 visitors, and nearly 10,000 professionals from around the world attend its conference, ADE Pro.
Maria Jiménez, an American music journalist who had moved to the Netherlands, is widely seen as the person who came up with the idea.
Conamus, the music organisation then led by John de Mol senior, put up 60,000 guilders for the first edition, about 28,000 euros today.
Gary Smith, a British journalist who worked for Conamus, recalls De Mol asking whether dance was really music at all just before he signed.
Former ADE director Richard Zijlma remembers a budget of 250 guilders to decorate the hall with disco balls and feathers.
The 100-guilder pass also opened the doors of RoXY, iT, Paradiso and the Melkweg.
The organisers say much of the music world dismissed dance, and the city would not even let them hang flags because it did not see ADE as a cultural event.
A conference ticket now costs around 700 euros, but the night programme has long overshadowed the daytime conference.
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