From the Han Yang University hospital's computer memory bank contaning the CT scans of over 3000 patients, 400normal patients between age of 1 to 69 years were selected at random. These scans were performed as a screeningtest in patient with minimal, vague neurologic manifestations such as headache, dizziness, convulsion anddepression or suffereing the traffic accdient. Determination of ventriculocerebral ratio vetween the width ofbrain and dimension representing the distance between the outer border of the lateral ventricle was made at thetwo sites, using the image 4 or 5 at the demonstrating the level of Monro's formen. In this paper, the 1stventriculocerebral ratio is defined as ; The maximum bifrontal diameter/The inner diameter of the skull at thesame level the 2nd ventriculocerebral ratio is defined as; The minimum bicaudate diameter/The inner diameter ofthe skull at the same level The ventriculocerebral ratio as measured by an actual distance marker at the appearingimage at the display terminal monitor are correlated with age and sex, and provided. This ratio seems to be areliable indicator of ventricular size and also help in comparing degree and judgement of treatment ofhydrocephalus The results are as follows; 1. The maximum bifrontal diameter of the normal frontal ventricle variesfrom 18.1% to 37.6% brain whidth B and its mean value for all age was 29.8% with a standard deviation of 1.9%. 2.The minimum bicaudate diameter of the normal frontal ventricle varies from 7.4% to 21.6% of brain width D and itsmean value for all age was 13.5% with a standard deviation of 1.1%. 3. The interesting tendency of the maximumbifrontal and minimum bicaudate diameter of the normal ventricle to increase with age were revealed. 4. Theventriculocerebral ratio of male group were tend to minimally increase or identify incomparision to the female group.