Extreme racing involves paddling a kayak down a section of hard whitewater requiring excellent boat handling skills. The rivers are typically grade 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 to IV rivers. Whitewater racing boats would be unsuitable for rivers used in extreme races. The rivers used in extreme races would be considered too difficult and dangerous for whitewater racing, and 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.

Extreme races are held on the Nevis in Scotland, and the Ulla in Norway.