The past year has seen important contributions made to resolving how chromosomes attach to and move on the mitotic spindle of animal cells. These include the findings that: kinetochore microtubules are derived from the asters (i.e. centrosomes); poleward chromosome motion need not be coupled to kinetochore microtubules disassembly; the motor for poleward chromosome motion is associated with the kinetochore; and immunological evidence that this motor is cytoplasmic dynein.