Previous experiments have established that visual stimulation in the roll plane causes people to feel roll vection. However, few experiments have been aimed at characterizing the relationship between changes in the subjective visual vertical (SVV) and the generation of vection. In this experiment we investigate the relationship between SVV, a quasi-subjective parameter, and vection, the visually induced perception of selfmotion. We observed three different patterns of change in SVV. Even with fixed visual stimuli, in many cases SVV changed continuously. These results suggest that conflicts among different sensory inputs produce dynamic changes in the priority of these sensory inputs. The longer vection is perceived, the more predominant the visual sensory input becomes.