Hearing loss, auricular anomalies and middle ear infections are common findings in many genetic disorders, but the mechanisms have remained unknown. We studied ear and hearing problems in Turner's syndrome (TS) in relation to the degree of X chromosome loss (i.e. degree of mosaicism) and growth. One hundred and nineteen girls and women with TS were studied regarding audiometry, fluorescent in situ hybridisation, serum concentration of insulin-like growth factor-1 (IGF-1) and body height. It was found that sensorineural hearing loss and occurrence of auricular anomalies were significantly increased the greater the proportion of 45,X cells in a particular individual (P<0.05 and P<0.001, respectively). Middle ear infections and sensorineural hearing loss were negatively correlated with IGF-1 (P<0.05 and P<0.001, respectively). Hearing correlated positively with height (P<0.01) and IGF-1 independently of age (P<0.05). Height correlated positively with IGF-1 (P<0.001). Auricular malformations, middle ear infections and hearing impairment in TS were interpreted as due to growth disturbances during development. A new hypothesis on the pathophysiology of external, middle and inner ear disorders due to a delayed cell cycle caused by chromosomal aberrations per se and not only to the specific X chromosome deletion is presented.