The objective of the present study was to estimate the prevalence of hyperacusis among school-aged children. We define hyperacusis as lowered loudness discomfort levels (LDL) associated with an abnormal annoyance to sounds. We used questionnaires, interviews, and estimates of LDL in a study of 506 children from 5 to 12 years of age from 15 different schools. Participants with LDL in the lowest 5th percentile were classified as having loudness hypersensitivity; an abnormal annoyance to sounds if they responded "yes" to the question "Are you bothered by any kind of sounds or noise?" could describe the sound, and were able to identify at least 10 sounds from a list of 20 as being annoying. Phonophobia was defined as a fear of sound. Children with LDL in the lowest 5th percentile typically had LDLs lower than 90 dB HL; 42% of the participants in this group were bothered by sounds and 3.2% had hyperacusis. Fifty percent of the participants with hyperacusis had tinnitus and mild hearing loss in the left ear was an associated risk factor. Phonophobia was experienced by 9% of the children. It is concluded that hyperacusis in children is prevalent, and should be considered in clinical examinations.