The idea of the IChO emerged at the Czechoslovak National Olympiad in 1968, where observers from Hungary and Poland were present. These three countries participated in the first IChO which took place in Prague, in 1968. In 1971, no IChO was held.
The 34th IChO was hosted by The Netherlands in Groningen on July 5-14, 2002.
The 33rd IChO was hosted by India in Mumbai (Bombay) on July 6-15, 2001.
The 32st IChO was hosted by Denmark in Copenhagen on 2-11 July, 2000.
The 31st IChO was hosted by Thailand in Bangkok on July 4-11, 1999.
The 30th IChO was hosted by Australia in Melbourne on July 5-13, 1998.
29th IChO (1997)
28th IChO (1996)
27th IChO (1995)
The 27th IChO was hosted by China in Beijing on July 12-20, 1995.
26th IChO (1994)
Home page for the 26th IChO held in Olso, Norway, on July 3-11, 1994.