Neurophysiologic and behavioral assessments of auditory function were performed on 224 very low birth weight (less than or equal to 1500 gm) infants requiring intensive care in the nursery. The subjects were studied prospectively from 36 weeks to 4 years of age, as available for follow-up. To classify them according to their neonatal status, we applied a principal components analysis to a number of variables representative of the extent of illness and of patient care in early postnatal life. The subjects were then divided into neonatal status quartiles and evaluated for hearing outcome. All those with sensorineural hearing loss fell exclusively into the lowest neonatal status quartile. Sensorineural hearing loss was statistically associated (1) with greater amounts of furosemide administration for longer durations and in combination with aminoglycoside antibiotics and (2) with more episodes of low pH, hypoxemia, or both, higher total bilirubin levels, and substantially lower neonatal status scores. Birth weight, gestational age, highest creatinine level, Apgar score, and aminoglycosides alone were not systematically related to hearing capacity. Subjects in the lowest neonatal status quartile also had a considerably higher incidence of middle ear disorders, characterized by elevated thresholds and prolonged auditory brain stem-response latencies reflective of conductive hearing loss. We conclude that protracted illness and its associated treatment, independently of specific diagnostic categories, constitute important risk factors for permanent hearing loss and for transient hearing loss in early life.