The legacy of an Olympic Games in a host city or country can take a variety of forms, including non-sporting benefits, such as enhanced urban infrastructure and national and international tourism profile, and sporting benefits, such as improved sporting facilities, strengthened sports organisations and potential increases in grassroots sport participation. This paper concentrates on the last of these, particularly in regard to the Sydney 2000 Olympic Games. The paper examines claims by the Olympic movement concerning increased sports participation as a legacy and examines available evidence to consider whether the hosting of the Games boosted sports participation in Australia. While some estimates suggest that participation did increase following the hosting of the 2000 Olympics, the failure of relevant organisations to maintain an adequate and consistent data collection regime makes this conclusion extremely speculative. From 2001 onwards, with the existence of a more stable data collection system and increasing awareness of the idea of a sport participation legacy, it is possible to make more reliable estimates of the pattern of grassroots sports participation following the hosting of the 2003 Rugby World Cup and the 2006 Melbourne Commonwealth Games. However, even when reliable and consistent participation data are available, the question of causality in the context of the wider sport development and participation system remains to be addressed.