Herewith we investigate the influence of semicircular canal (SCC) stimulation on the SVV by rotating normal subjects in yaw about an earth-vertical axis, with velocity steps of Ϯ 90°/s, for 60 s. SVV was assessed by setting an illuminated line to perceived earth vertical in darkness, during a per-and postrotary period. Four head positions were tested: upright, 30°backward (chin up) or forward, and ϳ40°f orward from upright. During head upright/backward conditions, a significant SVV tilt (P Ͻ 0.01) in the direction opposite to rotation was found that reversed during postrotary responses. The rotationally induced SVV tilt had a time constant of decay of ϳ30 s. Rotation with the head 30°forward did not affect SVV, whereas the 40°forward tilt caused a direction reversal of SVV responses compared with head upright/backward. Spearman correlation values (Rho) between individual SCC efficiencies in different head positions and mean SVV tilts were 0.79 for posterior, 0.34 for anterior, and -0.80 for horizontal SCCs. Three-dimensional video-oculography showed that SVV and torsional eye position measurements were highly correlated (0.83) and in the direction opposite to the slow phase torsional vestibuloocular reflex. In conclusion: 1) during yaw axis rotation without reorientation of the head with respect to gravity, the SVV is influenced by SCC stimulation; 2) this effect is mediated by the vertical SCCs, particularly the posterior SCCs; 3) rotationally induced SVV changes are due to torsional ocular tilt; 4) SVV and ocular tilts occur in the "anticompensatory," fast phase direction of the torsional nystagmus; and 5) clinically, abnormal SVV tilts cannot be considered a specific indication of otolith system dysfunction.