Squalene is a naturally occurring polyprenyl compound primarily known for its key role as an intermediate in cholesterol synthesis. It received its name because of its occurrence in shark liver oil (Squalus spp.), which contains large quantities and is considered the richest source of squalene. However, it is widely distributed in nature, with reasonable amounts found in olive oil, palm oil, wheat-germ oil, amaranth oil, and rice bran oil. The primary therapeutic use of squalene currently is as an adjunctive therapy in a variety of cancers. Although epidemiological, experimental and animal evidence suggests anti-cancer properties, to date no human trials have been conducted to verify the role this nutrient might have in cancer therapy regimens.