The yeast Saccharomyces cerevisiae has been used as an experimental model for the genetic and molecular dissecton of the aging process for the past decade. This period has seen the implication of some 30 genes in yeast aging. These genes encode a wide array of biochemical functions, suggesting the participation of multiple molecular mechanisms of aging. However, four principles appear to be at play: metabolism, stress resistance, gene dysregulation, and genetic instability. They unite the broad physiological aspects of yeast aging with those in other species. Genes and environment are not the only players; stochastic change also appears important in determining life span. This element of chance provides opportunities for an integrative approach, which is beginning to appear in yeast aging research.