Methods are presented for preparing cytoplasmic extracts from Xenopus laevis eggs and their utilization to reconstitute and monitor events of the cell cycle in vitro. Addition of sperm nuclei to crude extracts and "cycling" of the reaction through interphase and back into metaphase promotes formation of bipolar spindles capable of segregating their duplicated chromosomes. Reactions can be "spun down" onto cover slips for immunofluorescence analysis. High-speed extracts support mitotic chromosome condensation, which can be observed live by fluorescence time-lapse video microscopy. Because of the biochemically accessible nature of the egg extract system, a wide array of biochemical techniques can be combined with spindle and chromosome assembly reactions to evaluate the roles of specific proteins in these processes.