The size of spinal canal is valuable ot detect the body encroachment of spinal canal and expansion due totumors by computed tomography. This study was desinged for taking accurate measurement of the normal thoracicspinal canal in korean adults. The anteroposterior diameter, interpediculate distance and cross-sectional area ofthoracic spinal canal were measured in 80 normal adults. The results were as follows. 1. In A-P diameter, middleparts of the canal were smaller values than those of upper and lower parts from T1 to T6, and upper parts of thecanal were larger than those of middle and lower parts from T7 to T10. 2. In interpediculate distance, middleparts of the canal revealed larger value than those of upper parts. 3. All measurements of male were larger thanthose of female at all levels of the spinal canals and 65 measurement(93%) were statistically significant.