Although much progress has been made in understanding the events that lead to successful cell division, many details of this process remain a mystery. This dissertation presents findings which help to explain events that occur in the latest stages of cytokinesis, with an emphasis on the role of centrosome proteins. The first chapter introduces the novel centrosome protein centriolin. We show that this protein is localized specifically to the subdistal appendages of the maternal centriole in interphase, and it localizes to the midbody during cytokinesis. Disruption of this protein results in a unique cytokinesis defect in which cleavage furrow formation and ingression appear normal, but the cells remain connected by a thin intracellular bridge for extended periods of time. These results lead us to the conclusion that centriolin has an important function in cytokinesis. The second chapter describes our attempt to identify centriolin interacting partners. A yeast two hybrid screen was performed, and the results of this screen revealed an interaction between centriolin and proteins involved in vesicle target specificity and fusion. Further studies of these proteins revealed a novel localization to the midbody in cycling cells and a novel function in the final stages of cytokinesis, similar to centriolin. The third chapter discusses my attempts to clone and characterize a novel GTPase Activating Protein (GAP), which was also discovered in the screen for centriolin interacting proteins.