Williams syndrome is a true multiple congenital anomalies mental retardation syndrome affecting the vascular, connective tissue and the central nervous system. Affected individuals have a distinctive neuropsychological profile characterized by extremely poor visuospatial skills but relatively preserved verbal skills. A very striking characteristic is the hyperacusis or over-sensitivity to particular sounds. Klein et al. (4) found high rates (95%) of auditory over-sensitivity in a sample of Williams patients. The cause and mechanisms of auditory-over-sensitivity in Williams syndrome remain unclear. Some association has been suggested between hyperacusis and the occurrence of otitis media and also between hyperacusis and hyperactivity. The present study reports the results of an investigation into the occurrence of hyperacusis, otitis media and hyperactivity in a large group (N = 82) of Dutch speaking subjects with Williams syndrome from Belgium and The Netherlands. Prevalence and characteristics of hyperacusis and co-occurrence with otitis media and hyperactivity will be discussed and some management strategies are offered.