It still remains difficult to understand the three-dimensional anatomical relationships of such organs as ossicles, facial nerve, and skull base. At present, there is no alternative but to resort to two-dimensional CT and MRI. Helical CT now provides for three-dimensional representation of the temporal bone. The present study is an attempt to obtain three-dimensional images of the temporal bone by helical CT. Three-dimensional representation of the temporal bone making it easy to obtain an understanding of their stereoscopic structure. Our results will be presented, using video images. Method: In the CT study, the OM line was referred. The scan was performed with a helical scanning high-speed x-ray CT scanner (X-Vigor, Toshiba, Tokyo, Japan) using 150 mA, 135kv, 1-mm collimation, 0.8-mm-per-second table speed. Image was sent via a local area network to a workstation (X-tension, Toshiba, Tokyo, Japan). Three-dimensional image was obtained by the method of volume rendering technique at 0.2-mm reconstruction interval. Result: The motion picture which was obtained by processing three- dimensional CT images provided an adequate demonstration of the anatomical relationship between mastoid air cells and facial nerve canal, the anatomical relationship between skull base and attic, and the direction and position of semicircular canal. Helical CT permits a sufficient study of the operative field before operation and provides a useful tool for education in anatomy