The significance of measurement of the spinal canal size was well recognized in case of detection of intraspinal tumor as well as diagnosis of spinal stenosis. The measurement of sagittal diameter of the lumber spinal canal by plain x-ray film is not always easy. However, the new method designed by Eisenstein made the measurement of sagittal diameter of the lumber spinal canal by plain x-ray film very easy. In order to study the range of normal values of the sagittal diameter of lumber spinal canal in Korean adults, authors measured antero-posterior and transverse diameter of the lumbar spinal canal in 290 normal Korean adults by Eisensteins method. The results obtained are as follows: 1. Mean values of sagittal diameter of the normal Korean adults male was 17.37±1.05mm at Ll, 16.43±1.12mm at L2, 15.89±1.20mm at L3, 15.45±1.24mm at L4, and 17.34±1.13mm at L5 vertebra and in female, 17.41±1.23mm at Ll, 16.45±1.20mm at L2, 16.14±1.41mm at L3, 15.40±1.32mm at L4, and 17.25±1.20mm at L5 vertebra. 2. Mean values of transverse diameter of the normal Korean adults male was 23.54±1.18mm at Ll, 24.61±1.17mm at L2, 25.78±1.41mm at L3, 27.72±1.86mm at L4, and 30.42±2.23mm at L5 vertebra and in female, 23.06±1.45mm at Ll, 23.90±1.48mm at L2, 25.21±1.53mm at L3, 26.62±1.88mm at L4, and 29.70±2.41mm at L5 vertebra. 3. In transverse diameter, it was increased more and more to the lower lumber level, the widest at L5 vertebra. 4. In sagittal diameter, it was decreased less and less to the lower lumbar level, the narrowest at L4, and increased again at L5 vertebra. 5. The difference of sagittal and transverse diameter of lumbar spinal canal at each level of lumbar spine was very significant statistically. 6. The difference of the transverse diameter of the lumber spinal canal between male and female was significant statistically but that of the sagittal diameter was not. 7. The difference of the sagittal and transverse diameter between each age group was not significant statistically.