A new general registration method for images of different nature is presented. As gray levels or textures cannot be used for the registration of images from separate spectral bands, an edge-based method has been developed. Edge images are processed to extract straight linear segments, which are then grouped to form triangles. A set of candidate transformations is determined by matching triangles from the source and destination images. The transformations are then evaluated by matching the transformed set of source segments to the set of destination segments. As the coincidence of vertices or edge overlapping cannot be assumed in the registration of images of different nature, a new function for evaluating the matching quality between source and destination segments that does not rely on overlapping measures is proposed. Results and subjective evaluation of the registration of visual and thermal infrared images are presented.