We retrospectively investigated the influence of gestational age, perinatal risk, and the duration of incubator care periods in 193 surviving preterm infants with a gestational age between 28 and 36 weeks raised in our intensive care nursery incubators from 1965--1967. 24 (12.4%) of the children showed definite neurosensory hearing defects, which were particularly encountered in the high frequencies. No correlation could be substantiated between hearing difficulties and hyperbilirubinemia, streptomycin application and gestational age. This study does not support the assumption that the duration of noise exposure in currently used incubators is a major determinant for the development of deafness in otherwise healthy preterm infants. Our study did show, however, a strong correlation between the sum of all perinatal risk factors and neurosensory hearing loss.