Extreme racing involves paddling a kayak down a section of hard whitewater. The rivers used for this activity are typically class V and involve waterfalls and dangerous rapids. Races may involve mass-starts or individual timed runs.
By comparison, whitewater racing involves racing specialised canoes or kayaks down grade II[which?] to IV[which?] rivers. Whitewater racing boats would be unsuitable for rivers used in extreme races and thus are beyond the ability of the majority of whitewater kayakers.
Extreme races are often run as part of whitewater kayaking events. For example, the Ulla Extreme Race is part of the Sjoa Kayak Festival in Norway.