Abstract Mitotic PtK1 cells were treated at furrow initiation with microtubule poisons to determine the role of microtubules in the regulation of terminal cytokinetic events. The administration of anti-microtubule agents in late anaphase accelerated the rate of cytokinesis by approx. 60% as measured by changes in furrow diameter. Application of colcemid, nocodazole, or vinblastine sulfate to cells at furrow initiation all increased the rate of furrowing. Nocodazole, applied at various concentrations, demonstrated a dose-dependent relationship with furrowing rate. These results suggest a coupling between the disorganization and depolymerization of microtubules and the acceleration of furrowing. Electron microscopic analysis of cells treated with microtubule inhibitors show approx. 70% fewer microtubule profiles in the constricted region between the daughter cells. Microtubules may play a restraining role in the rate of furrowing.