Individual cells of the budding yeast, Saccharomyces cerevisiae, have a limited division capacity and undergo characteristicchanges as they senesce, primarily increasing both their cell size and cell cycle time. The mortality curve for ageing yeast cells can be described by the Gompertz equation, the classical definition for an ageing population. Recent work from several laboratories has demonstrated that genes can determine the yeast lifespan. Studies with the UTH genes have implicated changes in transcriptional silencing during yeast ageing, but the roles of the RAS2, LAG1 and PHBl genes in regulating yeast longevity are still unclear. What is becoming clearer, however, is that yeast ageing is more than just a bud scar phenomenon.