This study shows that the small GTPase RAB5, which is known to regulate early steps of endocytosis, also plays a part in mitosis. Depletion of RAB5 by RNA interference in human cell lines led to impaired chromosome congression and delayed nuclear envelope disassembly. Chromosome movements are largely mediated by kinetochores, which link centromeric chromatin to microtubules; consistent with this, RAB5-depleted cells showed decreased kinetochore tension and attachment to microtubules. These defects were caused by reduced accumulation of the centromere-associated protein CENPF at kinetochores, indicating that RAB5 regulates this process. Indeed, the authors found that RAB5 and CENPF form a complex around the nuclear envelope. On the basis of their findings, the authors propose that, by interacting with CENPF, RAB5 controls its accumulation at kinetochores after nuclear envelope disassembly has occurred.