Cephalograms are clinically useful for cephalometric diagnosis and superimposition. The measurements for cephalometry has always been done manually in practice. The purpose of this paper is to develop a cephalometric analysis system which can be used to improve the measurements by computer software. The software was developed as a Multi-Document Interface (MDI) application under the environment of Microsoft Windows. Two kinds of image, cephalograms and tracing papers, were supported. Three modules were included. Automatic landmarking module locates landmarks on the digitized cephalograms. Manual landmarking module provides the function manual to locate the landmarks on the screen through the interactive user interface. Cephalometric analysis module calculates the measurements. In our experiences, it has been shown the system turn out to be a handy tool for orthodontists in diagnosis and treatment.