OBJECTIVE The purpose of this study is to provide a new method to locate the foramen rotundum (FR) based on the structures in the wall of sphenoid. METHODS Computed tomographic angiography images of 172 FR in adults and 10 bony specimens were reviewed. The measurement was on coronal, sagittal, and axial planes after multiplanar reconstruction. The diameter, length, and direction of FR were measured. The middle lowest point of sellar region, the sagittal midline, and the bottom of sphenoid sinus were selected as the landmarks to locate the FR. RESULTS The FR can be found and identified easily on computed tomographic angiography image. The bony diameter measured in CT image is in accordance with that in specimen. The anterior opening and posterior opening can be located by the stationary structures in the sphenoid sinus. CONCLUSIONS The FR is a stationary bony structure; its length, diameter, and angle are relatively constant; and it can be easily located by the data measured in this study. The FR should be protected in the process of transsphenoid approach as well as be precisely located by the procedure about it.