This chapter provides a brief background on intraflagellar transport (IFT) and reviews the studies culminating in the identification of the dynein motor that powers retrograde IFT. IFT is the active movement of multi-subunit particles along axonemal doublet microtubules in the space between the outer-doublet microtubules and the membrane of cilia and flagella. Following this, it describes the known subunits of this dynein, discussing their specific functions, and examining how they fit together in the intact motor. Furthermore, it discusses the function of the dynein in recycling IFT proteins and other flagellar components, in transporting signals from the cilium to the cell body, in ciliary maintenance, and so on. Finally, it states that the basic function of cytoplasmic dynein 2 as the motor for retrograde IFT is now well established, and its general molecular architecture can be accurately predicted. However, much remains to be learned about this unique and important dynein. The currently intense focus on investigating ciliary function and assembly (and disassembly) is likely to provide more information on the role of dynein 2 in the transport of specific proteins and signals out of the cilium. Whether dynein 2 functions as a microtubule motor in other places where IFT particles are found besides the cilium is an important question that has yet to be addressed.