We have developed a system for the 3-D localization of anatomical structures without the need for surgical exposure by using multiple-view fluoroscopy images. In this paper, we describe the system and evaluate its application to the estimation of optimal imaging orientations in fluoroscopy. For positional measurement, a voxel-based 2-D/3-D registration technique was employed. Since the measurement condition depends on the object shape, spatial distribution of X-ray absorption, and overlap of organs or structures (which differs at each imaging position), determining the optimal combination of fluoroscopy orientations is significant. We propose a system for preoperative determination of the optimal imaging orentation by using the accuracy estimation of stereo localization from single-plane localization results. In an experiment, the computation time needed was 10 hours, which was about 14 times shorter than the time required for a full search of imaging orientation combinations.