Mitotic chromosome segregation is an essential process by which duplicated genomic information is transferred from mother to daughter cells. This process is accomplished by the spindle, a highly dynamic, microtubule (MT)-based structure. In each mitotic cycle the spindle undergoes a well-programmed set of morphological changes coordinated in time and in space. Molecular motors from the kinesin superfamily, which bind and move along MTs by hydrolyzing ATP, play central roles in mediating spindle dynamics. Our long-term goal is to understand how kinesin-related motor proteins perform their multiple mitotic functions and how is their activity regulated. To achieve this goal, we combine biochemistry, biophysics, cell biology, molecular biology and genetics to study mitotic kinesin motor functions and regulation.