Twenty infants, diagnosed by cranial ultrasound as having extensive cystic leukomalacia, had visual evoked responses (VER) and electroencephalograms (EEG) in the neonatal period and MRI scans later in infancy. The early ultrasound findings and results from the electrophysiological tests were correlated with later MRI findings and functional abilities. In infants with periventricular leukomalacia (PVL), the cysts were usually no longer visible by ultrasonography, beyond 40 weeks postmenstrual age (PMA), but later MRI scans showed a consistent pattern of delayed myelination around the irregularly dilated occipital horns of the lateral ventricles. VER's were present in the neonatal period and vision was maintained, although all infants developed a marked squint. EEG's were either normal or abnormal initially, but improvement was noted within several weeks. In those with subcortical or mixed lesions, cysts were noted to persist beyond 40 weeks PMA. Later MRI scans showed very poor myelination, with poor progress on subsequent scans and cortical atrophy. VER's were absent and all infants later became cortically blind. EEG's were severely abnormal and recovery was very poor. The infants with PVL developed spastic diplegia with moderate developmental delay, while those with mixed or subcortical lesions developed quadriplegia with severe mental retardation. An integrated approach, consisting of ultrasound imaging and electrophysiological recordings in the neonatal period and MRI imaging later in infancy, may provide a more reliable prediction of the pattern of later deficits.