High resolution real-time ultrasound scans were obtained through the anterior fontanelle to measure the lateral ventricles of 540 neonates of various gestational ages. Coronal scans showed that the distance between the falx and the lateral wall of the body of the lateral ventricle (ventricular index) and the greatest axis of the lateral ventricle (ventricular axis) were correlated with increasing gestational age. Growth charts were constructed for neonates of various gestational ages, from 24 to 40 weeks. The greatest distance perpendicular to the ventricular axis was defined as the ventricular depth. The depth of normal lateral ventricles was 0.18 cm (range, 0.13-0.23 cm). Hopefully, the data concerning ventricular sizes obtained in this survey can be utilized for the early diagnosis and control of posthemorrhagic ventriculomegaly.