Cell cycle progression is tightly regulated to prevent uncontrolled growth and division. Specific cell cycle factors are responsible for driving the cell from one cell cycle stage to the next. Many of these proteins are targeted for degradation by the ubiquitin proteasome system when their function is no longer required or may disrupt cell cycle progression. Here we describe a series of experiments used to study the ubiquitinmediated degradation of cell cycle proteins. This collection of assays may be used to determine the requirement for individual proteins in the degradation and ubiquitination of cell cycle proteins in Saccharomyces cerevisiae.