Recently, the demand for cosmetic rhinoplasty has increased because of a higher frequency of industrial accidents, trauma, and improved socioeconomic status. The lateral osteotomy is one of the essenital procedures in corrective and reduction rhinoplasty. Two significant problems can be encountered during lateral osteotomy. One is injury to the nasolacrimal duct when the osteotomy is performed too close to the orbital margin. The other is the incomplete correction due to excessively medially directed the osteotomy. Nevertheless, safer and more complete standardization of lateral osteotomy has not yet been made. In order to eatablish the criteria for lateral osteotomy, several variables were measured by hands with vernier calipers and by Computed Tomography(CT) in 37 dry skulls. The results have shown that the area most vulnerable to injury is the bony dehiscent portion of the nasolacrimal duct, located just beneath the medial canthal ligament. The nearest area to the nasolacrimal duct in the entire nasomaxillary groove was found to be the most inferomedial wall of the orbit which is approximately 3mm apart from the duct. The nasomaxillary groove, which needs to be fractured, was found to begin just above the attachment of the inferior turbinate and to end at the nasion. These landmarks were confimed on the cadaver. The results suggested as follows; 1) Lateral osteotomy should begin just above the attachment of the inferior turbinate. 2) It seems safe to perform a lateral osteotomy 3mm medial to the side of the inferomedial wall of the orbit along the nasomaxiilary groove. 3) It is preferable not to perform an osteotomy in the region above the nasion. 4) For a complete osteotomy, the angle of the osteotome in relation to the maxillary bone should be maintained at 30 degrees.