Various measurements of cerebral ventricles in 50 normal newborn infants were performed, using ultrasonography. In transverse scan using linear array realtime scanner with 3 MHz transducer, the ratio of the distance between the falx and lateral wall of lateral ventricle to the hemispheric width was measured. In coronal scan through the anterior fontanelle using gray scale B-mode scanner with 5 MHz transducer, the ratios of the bifrontal diameter of the lateral ventricles to externally measured biparietal diameter and to head circumference were measured. Width of frontal horn at 5mm distance from the lateral end of frontal horn was also measured. In addition, the presence of cavum septi pellucidi was investigated in coronal scan. The result are as follows: 1. The lateral ventricle/hemispheric width ratio in transverse scan was 0.31$pm$ 0.03. 2. Bifrontal diameter of lateral ventricle/biparietal diameter ratio was 0.20$pm$0.02 and bifrontal diameter of lateral ventricle/head circumference ratio was 0.054$pm$0.006. 3. Width of frontal horn was about 1mm and maximum width was 2mm. 4. There was no significant difference in ventricular size between male and female, and among different gestation ages. 5. Cavum septi pellucidi was found in 44 neonates (88%) among 50 normal neonates in coronal scan.