Estimation of liver size is essential in the diagnosis of liver disease, Many approaches have been attempted in evaluation of liver size such as the measurement of length, area and volume. Among these, area and volume measurements are accurate but complicated, so we commonly use formerly introduced various linear measurements, but in scintigraphy one must calculate the actual liver size using rate of reduction, which is time consuming. Because of these reasons, we carried out present study to represent liver size by means of a simple liver measurement like we express the cardiac size by cardiothoracic ratio. Our cases consisted of 100 clinically normal subjects as the normal group and 50 patients suffering from liver disease and diagnosed to have hepatomegaly on abdominal palpation and scintigram at Dept. of Radiology of St. Mary's Hospital, Catholic Medical College during the period of 8 Months from Jan. 1980. We Measured the liver size using 4 linear diameters(Fig. 1). And as the reference measurement, the distance from the right margin of the liver to the left margin of the spleen was measured. We called this "abdominal transverse diameter(ATD)". The results were as follows;1) The smallest value was recorded in the midline vertical diameter(MVD). It was 4.2±0.4cm in normal group and 5.0±0.6cm in the hepatomegaly group. 2) The diameter using other methods ranged from 5.6 to 7.2cm in the normal group and from 6.3 to 7.5cm in the hepatomegaly group. 3) There was significant difference in the ratio of each diameter to ATD between the normal and hepatomegaly group(〈0.0l). We called this "hepato-abdominal ratio". 4) The "hepato-abdominal ratio" using MVD is 0.43±0.06 in the normal group and 0.53±0.07 in the hepatomegaly group. The "hepato-abdominal ratio" of MVD was most significantly different between normal and hepatomegaly group. 5) The tolerance limits(99%) of "hepato-abdominal ratio" using MVD is from 0.41 to 0.45 in the normal group and from 0.51 to 0.55 in the hepatomegaly group. Therefore, by reasons