A collection of basic cutting-edge techniques for studying the mechanisms underlying cell cycle regulation and checkpoint control. Using mammalian, yeast, and frog systems, these readily reproducible methods can be used to induce cell cycle checkpoints, detect changes in cell cycle progression, identify and analyze genes and proteins that regulate the process, and characterize chromosomal status as a function of cell cycle phase and progression. Each fully tested technique includes step-by-step instructions written by an investigator who routinely performs it, an introduction explaining the principle behind the method, equipment and reagent lists, and tips on troubleshooting and avoiding known pitfalls.