Fast axonal transport is manifested at the sub-cellular level as the anterograde or retrograde movement of membrane-bounded organelles along microtubules. Earlier work implicated the protein kinesin as the motor for anterograde axonal transport. More recent work indicates that a brain microtubule-associated protein, MAP 1C, is responsible for retrograde transport. Of additional interest, MAP 1C has been found to be a cytoplasmic form of the ciliary and flagellar ATPase dynein, indicating a much more general functional role for this enzyme in cells than had been suspected.