Hong Kong will stage the equestrian events in the 2008 Beijing Olympics.
The move had been opposed by the International Equestrian Federation, who said it would make them feel "separate" from the rest of the Games.
But Beijing officials had said the move was necessary because of "uncertainties of equine diseases".
IOC president Jacques Rogge said: "Everyone would have wished it could have taken place in Beijing, but sanitary problems made this very hard."
He added: "I wish to thank the FEI for having shown a great support for the Olympic movement in agreeing to this relocation. The IOC will do everything to ensure the event is a great success."
Beijing organisers have told equestrian chiefs that they will provide the best possible conditions for the horses and riders in Hong Kong with vice-president Wang Wei saying: "We are delighted that the best possible solution for the Beijing 2008 equestrian competition has been found."
A sports training ground and a park near the Shatin racecourse in Hong Kong will be converted into a competition venue.
Organisers will also install giant cooling fans along the course to meet fears that the heat and humidity may be lethal for the horses.