Purpose/Aim: Obstructive sleep apnea (OSA) is characterized by recurrent respiratory disorders associated with increased cardiovascular morbidity and mortality. The increment of systemic inflammation in OSA has been considered as the major pathogenic mechanism leading to cardiovascular diseases. There is limited and conflicting information in the literature investigating myeloperoxidase (MPO) activity and soluble tumor necrosis factor receptor-1 (sTNF-R1) levels in OSA patients. The aim of our study is to assess the clinical utility of plasma MPO activity and sTNF-R1 levels as risk markers for systemic inflammation and development of cardiovascular diseases in OSA patients. Materials and Methods: 59 OSA patients diagnosed with polysomnograhpy for Apnea-Hypopnea index (AHI), and 26 healthy volunteers enrolled into the study. Plasma MPO activity was measured using a spectrophotometric method. An enzyme-linked immunosorbent assay (ELISA) method was used to detect plasma sTNF-R1 levels. Results: Plasma MPO activity and sTNF-R1 levels were significantly higher (43.2 +/- 21.65 vs. 30.44 +/- 8.05 p =.0046; 2.379 +/- 1.2 vs. 1.086 +/- 0.86 p < .0001, respectively) in the total OSA patients compared to the control group. There was a significant weak correlation between MPO activity and disease severity indicator AHI (p = .03 r = .27). Conclusions: Elevated plasma MPO activity and sTNF-R1 levels in the OSA patients indicate increased systemic inflammation and oxidative stress which might contribute to the higher incidence of cardiovascular diseases. Therefore, we recommend measurement of plasma MPO activity and sTNF-R1 levels in the OSA patients as potential risk predictors for cardiovascular diseases.