Cell motility depends on rearrangement of the cytoskeleton. In chemotaxing cells, an external gradient of chemo-attractant is thought to be converted into a localized signal in the membrane, which directs actin polymerization and, consequently, formation of pseudopodia and forward movement. In Dictyostelium, motility depends on NSF – a protein that functions in vesicle docking/fusion – so could membrane trafficking also be involved? On p. 2318, David Traynor and Rob Kay investigate this possibility, following movement of starving Dictyostelium cells towards a cAMP source. They show that the cells maintain an active endocytic cycle but that this is not required to polarize the leading edges of the cells or to produce membrane flow (an alternative motive force that might drive cells forward). The authors then use confocal reconstructions to demonstrate that the surface area of Dictyostelium cells fluctuates by 20–30% during movement, a change that cannot be due to the stretchiness of the plasma membrane. They propose, therefore, that the endocytic cycle allows moving cells to change their surface area and thus produce the shape changes necessary for movement.