Mechanical imperfections, including misalignment of the sheaves, can signi"cantly in#uence the levels of vibration and noise that are produced in power transmission belt drives. In this paper, laboratory measurements identify a particular source of vibration excitation for v-belts that is attributed to lateral misalignment of the sheaves. The belt is shown to undergo a "ne, periodic, radial motion on the sheave at a frequency and amplitude that depend on the level of misalignment, the belt's bending sti!ness, pre-tension, and wedge angle, the sheave's radius, and the belt-to-sheave friction coe$cient, among other modelled variables. Periodic radial oscillation and slippage of the belt in this manner result from frictional stick-slip response at the belt/sheave interface. The belt experiences a prescribed sawtooth-like motion on its boundary, which is one source of its high-frequency vibration and noise. An optical displacement sensor is used to record motion of the belt on the sheave, and those measurements are correlated with the near-"eld sound pressure. A theoretical model is developed to describe boundary excitation of the belt as is caused by misalignment, and in particular to predict the frequency and amplitude of the boundary motion. The model's predictions are compared with measurements for parameter studies in the belt's pre-tension and in the sheave's radius.