This paper describes a method for camera motion estimation based on real endoscope images and CT images for an endoscope navigation system. We have developed an endoscope navigation system that shows the navigation information during an endoscope examination. In this system, we need to Out side view and estimate the real endoscope camera motion. Our method tracks the camera motion by using an imagebased registration technique. We applied the proposed method to the video images of the real bronchoscopy and 3-D X-ray CT images. Experimental results showed that the method could track the camera motion corresponding to the real endoscope Figure 1: Endoscope navigation system correctly.