Landmarks on the cephalograms are those representing the actual anatomic structures of the skull. These points are used by orthodontists for diagnosis and treatment planning. In this study, a microcomputer system with a desk-top scanner was employed for locating the landmarks of X-ray cephalogram automatidy. Fustly, the digitized image of cephalogram is processed to define a reference point for analysis, and divided into several rectangular subimages (such as frontal, orbit, mda, mandible,...). These regions containing all the useful landmarks are then enhanced in the preprocessing stage. The pyramid method is used to reduce the resolution of image, and the edges are detected by the appropriate edge detectors or the best orientation edge detector. The curve. of each edge is corrected elastically with the pre-stored models. Finally, positions of landmarks could be located immediately and the associated paremeters could also be computed for diagnosis.