To study whether elevated levels of bilirubin in the neonatal period increase the risk of developmental problems for very low birth weight neonates, the investigators used data from a geographically based sample of 495 very low birth weight neonates, born January 1, 1985, to December 31, 1989, who survived to 1 year of adjusted age. Maximum neonatal bilirubin levels were found in medical records. A developmental problem was defined as either cerebral palsy or a Bayley Mental Developmental Index of less than 68 at 1 year adjusted age. Potentially confounding factors were controlled using logistic regression. To control for the effects of intracranial abnormalities (eg, intraventricular hemorrhage), separate logistic regression analyses were carried out for three strata, defined according to the results of cranial ultrasonography. In these analyses, the following odds ratios (with 95% confidence limits) were found for the association of maximum neonatal bilirubin concentration and developmental problems: for subjects without intracranial abnormalities, 0.9 (0.7, 1.9); for subjects with uncomplicated intracranial hemorrhage, 1.5 (0.8, 2.5); for subjects with complicated intracranial hemorrhage or intraparenchymal echo-densities, 1.2 (0.4, 3.6). In summary, in analyses controlled for confounding factors, maximum neonatal bilirubin level was not consistently associated with the risk of developmental problems identifiable at 1 year.