Ether lipids of a novel type, the botryococcoid ethers, have been isolated from the green alga Botryococcus braunii grown in culture. Structures were assigned from spectroscopic analysis and chemical transformations. Botryococcoid ethers exhibit an oxygen bridge between two long hydrocarbon straight chains; in the three compounds a C27 alkadienyl secondary alcohol is linked, α to the hydroxyl-bearing carbon, via an ether bridge to a C27 alkatrienyl chain and to saturated n-C24 and n-C26 alkyl chains. Both carbons of the ether function are secondary in one compound, whereas in the others only one is secondary, the other one being primary. This type of component could be involved in the biosynthesis of algal biopolymers which exhibit great resistance towards non-oxidative chemical attacks and are thought to have played a major role in the fossilization of algal biomasses.