The aim of the study was to assess the markers of oxidant-antioxidant status in patients with obstructive sleep apnea syndrome (OSAS) who underwent uvulopalatal flap (UPF) surgery. Twenty-five patients who underwent UPF surgery participated in this study. Polysomnographic examinations were performed before and after the surgery to assess sleep apnea in all patients and to determine the success of the UPF surgery regarding the improvement in the apnea-hypopnea index (AHI). Descriptive factors (BMI, age, gender and neck thickness, etc.) of patients were recorded before operation. Blood samples were taken preoperatively, and repeated postoperatively at 6-month intervals to determine the changes in serum malondialdehyde (MDA) and matrix metalloproteinase-9 (MMP-9) levels. The mean age at surgery was 45.6 ± 9.9 years (range 25-63 years). There was a significant difference between preoperative and postoperative AHI, MDA and MMP-9 values (p < 0.05). There was no significant correlation between categorical variables. There was no correlation between postoperative ODI, MMP-9 and MDA. These results indicate that OSAS is associated with abnormal lipid peroxidation, which can be improved by UPF surgery. OSAS may increase risks of cardiovascular morbidity; however, UPF might be useful for decreasing these risks in patients with OSAS who are suitable candidates for UPF surgery. © 2013 Springer-Verlag Berlin Heidelberg.