1. Abstract 1.1.Background: A precise and reproducible lateral Osteotomy is a necessity for successful rhinoplasty. Generally, two basic techniques have been introduced: the external perforated method and the internal continuous method. There is an ongoing debate in the literature on the appropriateness of each method in terms of post-operative complications and patients’ satisfaction. Nasal mucosal tear is a key element in this comparison. This study was designed to compare the two techniques using a blinded endoscopic evaluation of the nasal mucosa tear after the osteotomies were performed by one of these two techniques. 1.2.Methods & materials: In a randomized clinical trial, 30 candidates for elective nasal surgery (aged 20-30 years) were studied in Tabriz Imam Reza Teaching Center during a 12-month period. Each patient underwent an external lateral Osteotomy performed on one side and an internal lateral osteotomy performed on the alternate side by a specialist with experience in the use of both types of osteotomy. In a blinded manner, another investigator used nasal endoscopy to detect nasal mucosal tears and reported them in millimeter (mm). 1.3.Results: A total of 30 patients, 10 males and 20 females with the mean age of 26.47±7.36 years (20-30) were enrolled in this study. Nasal mucosal tear was reported in all patients with internal lateral osteotomy, whereas this rate was 90% in the other group (p=0.24, odds ratio=1.11, 95% confidence interval=0.99-1.25). The median length of the mucosal tears was 9mm (Interquartile range, IQR=2) in the cases with internal osteotomy vs. 4mm (IQR=1) in the patients with external approach. The difference was statistically significant (p<0.001). The intra-group analysis stratified by the patients age and sex revealed a significant association neither with frequency nor with severity of the nasal mucosal tears. Conclusion: This study showed that internal osteotomy, as compared with external technique, is along with significantly more severe nasal mucosal damage in patients undergoing elective nasal surgery.