Yeast provides an attractive system in which to study proprotein processing. Many of their processing events are remarkably similar to those in higher eukaryotes and their amenability to experimental manipulation permits approaches that are not always feasible in multicellular organisms. Analysing the biosynthesis of the yeast mating pheromones has been particularly rewarding and has provided insights into both the proteolytic aspects of processing and other post-translational events such as prenylation and carboxymethylation.