In order to assess the importance of pertinent perinatal risk factors in causing hearing loss (HI), a retrospective evaluation was made of the records of 146 affected children born in the city of Göteborg between 1970 and 1979. The incidence among six-year-olds born between 1970 and 1974 was 3.8 per 1000 newborns. If only HI of more severe degree was taken into account (above 40dB in the best ear), the remaining incidence was 1.4/1000. Sensorineural HI (SNHI) accounted for 87 per cent of the cases. A positive hereditary tendency for HI was found in 55 per cent. In 61 per cent the origin of the HI was presumably prenatal, either positive heredity alone or in the form of facio-auricular anomalies, syndromes and toxic influences (infection and alcohol) during early pregnancy. Postnatal infections (meningitis, parotitis and secretory otitis media) could be ascertained as causes in about 20 per cent of the cases. For 12 per cent no aetiology could be determined. Perinatal aetiology was probable or possible in about 10 per cent of the children. The frequency of SNHI was found to be increased among survivors of neonatal intensive care, VLBW, LBW and SFD infants. Caesarean section, ventouse and breech delivery were not associated with increased rates, nor were hyperbilirubinaemia, exchange transfusion or birth asphyxia. No cases could be traced to aminoglycoside treatment. Neonatal sepsis/meningitis may have been the cause in two of the 146 cases. Hypoxia as a consequence of apnoea and respiratory distress syndrome necessitating mechanical ventilation appeared to be the major risk-factor in the neonatal period. However, in comparison with genetic predisposition, potentially damaging perinatal factors appeared to be of minor importance.