INTRODUCTION: The Epley maneuver is the recommended treatment for benign paroxysmal positional vertigo of the posterior semicircular canal (PC-BPPV). Traditionally, the angle of the patient's head in each position during the Epley maneuver is not monitored and subjectively estimated by physicians. As a result, deviations of head angles from the standard may affect the treatment result. This study aimed to compare the outcome of the Epley maneuver between the group of exact head angles and the group of subjectively estimated angles (traditional Epley maneuver). METHODS: A single-blind randomized controlled trial was conducted at the Department of Otolaryngology, Chiang Mai University Hospital. PC-BPPV patients were attached with the head angle measuring device and randomized into 2 groups: group I - the exact angle group, physicians performed the Epley maneuver with accurate head angle in each step
and group II - the estimated angle group, physicians performed the Epley maneuver by estimating the head angle (traditional Epley maneuver). The treatment outcomes were measured at 1 week in the aspects of negative Dix Hallpike results and severity of dizziness. RESULTS: Thirty-one PC-BPPV patients were recruited and randomized into group I (15 participants) and group II (16 participants). Both groups showed clinical improvement. Although significant deviations of head angles were observed in group II, there was no significant difference in outcomes between the two groups in terms of negative Dix Hallpike and severity of dizziness at the 1-week follow-up. CONCLUSIONS: Although significant variations of head angles were observed during the traditional Epley maneuver by experienced physicians, these deviations were slight (less than 15°) and did not significantly affect the successful treatment outcome at 1 week, in terms of negative Dix Hallpike and severity of dizziness, when compared to the group with accurate head angle during the Epley maneuver.