High resolution, real-time ultrasound scans were obtained through the anterior fontanelle to examine the intracranial anatomy of 100 neonates. Of 43 patients with abnormalities, 26 had intracranial hemorrhage (subependymal, intraventricular, or cerebral). Of the 51 patients also studied by CT, the sensitivity of ultrasound in detecting hemorrhage was 96% and the specificity 94%. This ultrasound technique was also very useful for detecting complications such as porencephalic and subependymal cysts, ventricular septations, and hydrocephalus. In normal premature neonates (25 to 35 weeks gestation) the lateral ventricles appear as slit-like structures on the coronal scan. The midline-lateral dimension of normal lateral ventricles was 8.6 mm (range 7-11 mm) and the depth of 1.9 mm (range 1-3 mm). Follow-up scans in patients with intraventricular hemorrhage show that in mild hydrocephalus, the lateral ventricle becomes rounded rather than slit-like. This change occurs before the midline-lateral dimension of the ventricle increases.