We investigate edge extraction and the segmentation of range images. We first discuss problems that arise in conventional region-based and edge-based segmentation methods, then we propose a new edge-based segmentation algorithm. In the proposed algorithm, we extract edge contours by using the Gaussian filter and directional derivatives and segment a range image by integrating detected roof and step edges. Thus the correspondence between step and roof edges is not necessary. Computer simulations with several range images show that the proposed edge-based range image segmentation method is simpler and yields better performance than the conventional methods.