A variety of flow cytometric methods have been developed over the past 25 yr to study how treatment with chemotherapeutic agents affects cell-cycle progression. One of the most commonly used measurements relies on a singletime analysis of the DNA distribution of a cell population (1 ). This analysis may also be multivariate, for instance, when another cell feature is measured in addition to DNA. The additional feature(s) often provides information about a particular metabolic or molecular feature of the cell that often correlates with the rate of cell progression through the cycle or cell quiescence. Therefore, although such measurements per se cannot reveal whether or not the cell actually progresses through the cycle, the kinetic information is inferred from the DNA content (cell-cycle position) and from the metabolic or molecular profile of that cell.