The size of spinal canal is measured to detect the lumbar spinal stenosis syndrome and expanding intraspinal tumors by computed tomography. This study was designed for taking accurate measurement of the normal lumbar spinal canal in Korean adults. The anteroposterior diameter, interpediculate distance and cross-sectional area of lumbar spinal canal were measured in 110 normal adults. The results were as follows: 1. The window center that showed identical value consistent with actual measurement of phantom was between + 160HU and + 240HU and the window width was below + 300HU. 2. In anteroposterior diameter, upper part of the canal was larger value than that of middle and lower parts, but in interpediculate distance, lower part of the canal revealed larger value than that of upper and middle parts. There was no significant difference in cross-sectional area. 3. All measurements of male were larger than those of female at all levels of the spinal canal and 42 measurements(58%) w re significant statistically. 4. compared with Americans, Korean showed lower value in anteropsterior diameter and cross-sectional area but higher value in interpediculate distance. 5. Above results should contribute to making an another criteria for diagnosing the lumbar spinal stenosis in Koreans.