Conclusion: Selected patients might have benefited from genioglossus advancement (GA), even it was applied solely. GA provided significant reduction on the apnea hypopnea index (AHI), with a 53% surgical success. Objectives: The aim of this study was to evaluate the impact of GA on AHI of patients with obstructive sleep apnea (OSA). Method: From January 2008 to April 2014 patients who underwent a genioglossus advancement procedure alone were included into the study and records of these cases were analyzed retrospectively. Pre-operative and post-operative values of body mass index (BMI), Epworth Sleepiness Scale (ESS), nocturnal polysomnographic data including AHI, mean, and minimum oxygen saturation were compared. Results: There were 16 males and one female patient with the mean age of 46 years. The AHI showed a significant reduction from 27.5 +/- 8 pre-operatively to 17.3 +/- 12.6 post-operatively. The pre-operative and post-operative mean O-2 saturation value improved from 92.1 +/- 2.4% to 93.4 +/- 1.7%. Pre-operative ESS scores decreased significantly from 7.7 +/- 1.6 to 4.8 +/- 1.9. There were no significant difference between pre- and post-operative values of BMI and minimum O2 saturation. The success rate was found to be 53%, which was based on success criteria as an AHI of <20 with at least 50% reduction.