The purpose of this study was to evaluate the effects of rapid maxillary expansion (RME) on conductive hearing loss in 35 subjects (21 girls and 14 boys) with an average age of 14 years 6 months. All patients had maxillary constriction with a high palatal vault and a conductive hearing loss. Pure-tone audiometric records were used to determine the hearing levels at four time intervals, namely, before RME, after sufficient midpalatal suture opening was obtained (mean: 18 days), after the retention period (mean: six months), and a final set two years after the retention period. Records were evaluated by the same otolaryngologist. Analysis of variance was used to assess the changes in the hearing level and the air-bone gap. Descriptive statistics were calculated for each subject at each period. The results indicated that significant changes occurred in both the hearing levels and air-bone gaps in both timing and frequency after the active treatment period (P < .001). For most patients (74%), these improvements were maintained two years after active treatment.