The attenuation values of the CT were measured by a dual energy technique, resulting in determination of theraw data of the region of interest. In our previous report, CT values were correlated to the bone mineral concentration. Repositioning error was insignificant in our dual energy CT. We studied cortical minearl contentsof L3 body in 120 healthy men and women. The results were as follows: 1. The bone mineral content on themid-anterior portion of L3 vertebral body was highest in fifth decade of 304±27mg/cc in men and 288±22mg/cc inwomen. 2. The bone mineral content on the right postero-lateral portion of the L3 vertebral dody was highest valuein fifth decade of 471±31mg/cc in men and 412±28mg/cc in women. On the left postero-lateral portion, highest in fourth decade of 504±40mg/cc in men and 438±42mg/cc in women. 3. The men values of the cortical bone mineral contents of L3 body were highest in fifth decade of 421±30mg/cc in men and in fourth decade of 365±34mg/cc inwomen.