Sphingolipids and their phosphorylated metabolites play crucial roles in intracellular signalling in animals, and evidence is emerging for analogous situations in fungi and plants. Central to this signalling pathway is the phosphorylation of the sphingoid long chain base, sphingosine, which yields sphingosine-1-phosphate. Until recently, the enzyme responsible for the biosynthesis of sphingosine was unknown, but the Delta(4)-long chain base desaturase that carries out this reaction has now been identified. Orthologues are present in animals, plants and fungi, raising the possibility of using reverse genetics to determine the contribution of sphingosine-1-phosphate to signalling networks.