Comparative morphology of the cement delivery apparatus of three lepadomorph barnacles indicates that the lepadid Lepas anatifera is unable to relocate voluntarily, whereas the two scalpellids Pollicipes pollicipes and Capitulum mitella can. Mean relocation speeds of up to 50 μm d−1 were measured for both scalpellids, which are probably underestimates of maximal rates given the absence of a directed stimulus. In the laboratory neither gravity nor unidirectional flow proved effective stimuli in directing scalpellid relocation. The two scalpellid species use quite different mechanisms to effect relocation at a leading edge of the base, although both slough basal material at the trailing edge. It is suggested that basal growth effectively accounts for the mobility of P. pollicipes but C. mitella is likely to employ muscular activity.