Microdeletion 22q11 (del22q11) is one of the most frequent causes of genetic syndromes. The majority of cases of di George and velocardiofacial syndromes are due to del22q11. These conditions are considered to be developmentally related to neural crest anomalies influencing the differentiation of the branchial arches, including the percursor tissue of the ear. In addition, the UFDIL gene, an ubiquination gene being expressed during embryogenesis in the inner ear primordia, has been identified in the 22q11 critical region. The aim of this study was to evaluate the prevalence of hearing impairment in del22q11 syndrome. Admittance audiometry, behavioural pure tone audiometry and auditory brainstem response (ABR) were performed in 27 children studied at our hospital between 1997 and 1998. Results were related to clinical history, frequency otitis media and immune status. Sensorineural hearing loss was found in 4/27 (15%) patients (severe in three cases, mild in one), conductive hearing impairment in 12/27 (45%) (moderate in four cases, mild in eight) and normal hearing in 11/27 (40%). Interestingly, three of the patients with sensorineural hearing loss had cerebral lesions due to neonatal distress, to hydrocephalus and to post-surgical ischaemia each in one. The prevalence of speech delay, otitis media and low CD3 values was higher among patients with conductive hearing impairment in comparison with those with normal hearing. In conclusion, hearing impairment was documented in 60% of the patients and must be included among the clinical features of del22q11 syndrome. Audiological evaluation is recommended in patients with del22q11 in order to reduce the risk of speech deficit.