The apogeotropic type of benign paroxysmal positional vertigo involving the horizontal canal (HC-BPPV) is likely due to otolithic debris in the anterior arm of the canal (canalithiasis) or the debris attached to the cupula (cupulolithiasis). It is important to seek the method to convert treatment-resistant apogeotropic form to the more treatment-responsive geotropic form in HC-BPPV. Recent randomized trials demonstrated that head shaking maneuver was more effective than the modified Semont maneuver and the Gufoni and head shaking maneuvers showed similar efficacy in treating apogeotropic HC-BPPV. Moreover, new repositioning maneuver using mastoid vibration showed good efficacies in patients with apogeotropic HC-BPPV in recent study. So we tried to compare the short term therapeutic efficacies of Gufoni maneuver and mastoid oscillation in apogeotropic HC-BPPV with a randomized, prospective, sham-controlled study.