Microtubules are responsible for chromosome segregation and the movement and reorganization of membranous organelles. Many aspects of microtubule-based motility can be attributed to the action of motor proteins, producing force directed toward either end of microtubules. How these proteins are targeted to the appropriate organellar sites within the cell, however, has remained a mystery. Recent work has begun to define the targeting mechanism for two well-studied motor proteins, kinesin and cytoplasmic dynein.