Envirothon includes up to three levels of competition: regional, provincial, and international.

Regional and provincial events take place during the spring, followed by the US-based national Envirothon, which is a five-day event scheduled within the first two weeks of August each year. The winning team from each region proceeds to the provincial event, and the provincial champions then have the opportunity to represent Ontario at the international competition, which is held at a new site each year. Participation is open to all students enrolled in grades 9 through 12 in public, private, occasional, technical, or home school programs, or community organizations such as Guides, Scouts, and other clubs.

Ontario Envirothon includes 5 subjects
-Aquatics -Forestry -Soils -Wildlife
And a Special Topic which changes annually. The special topic for 2003 is: Urban Sprawl and Agricultural Land Preservation.