Fifteen infants and children with clinical evidence of periventricular leukomalacia (i.e., spastic diplegia or quadriplegia and premature birth) were studied. Computed tomography (CT) scans of the brain demonstrated the following characteristic abnormalities: reduction in quantity of periventricular white matter, particularly at the trigone, deep and prominent sulci that abutted the ventricles without interposed white matter, and ventriculomegaly with irregular outline of the lateral ventricles. The location and severity of abnormalities on CT scans correlated well with the neurologic abnormalities observed at follow-up and the known anatomic location of periventricular leukomalacia. These observations demonstrate the diagnostic value of CT scanning for periventricular leukomalacia during late infancy and childhood. Although serial ultrasonography during the first weeks of life may be diagnostic of periventricular leukomalacia, it is of less value later. In contrast, CT scans obtained beyond 6 months of age can demonstrate a characteristic pattern of abnormalities that may be considered diagnostic of periventricular leukomalacia.