This study examined the auditory status of females with Rett syndrome (RS) using auditory brainstem response (ABR) testing and measures of acoustic admittance. Prevalence of hearing impairment in 81 female patients (age range 1 year 3 months to 39 years 8 months; mean age 8 years 7 months, SD 6 years 4 months) was evaluated with ABR measurements. If the ABR latencies at 20dB nHL exceeded those of the normative group, a slight hearing loss was diagnosed. For ABR thresholds in the range 30 to 40dB nHL, a mild hearing loss was determined; moderate hearing loss was diagnosed for ABR thresholds in the range 50 to 60dB nHL. Bilateral hearing loss was found in 16 (19.3%) patients and unilateral hearing loss in 13 (16%) patients. Bilateral hearing loss of moderate degree was found in one patient. No patient was found with severe hearing loss (ABR threshold of 70dB nHL and above) in either ear. Slight hearing loss was found in 10.5% of ears (17 of 162), mild hearing loss in 14.2% of ears(23 of 162), and moderate hearing loss in 3.1% of ears (5 of 162). In 72.2% of ears (117 of 162), findings indicated the presence of normal peripheral auditory sensitivity. Prevalence of sensorineural hearing loss was 17.3% (28 of 162). Evidence of conductive involvement (conductive and mixed hearing loss) was observed in 9.9% of ears (16 of 162). In this cross-sectional study, the prevalence of hearing loss was increased in older RS participants and in those with seizures requiring the use of anticonvulsants. Neither the type of hearing loss nor the presence of preserved speech seemed to be correlated with the type of mutation in methyl-CpG-binding protein 2 (MeCP2) gene that is associated with RS.