Background: We aimed to investigate relationship between gamma glutamyl transferase (GGT) activity with paraoxonase 1 (PON1) activity and aortic stiffness (AS) parameters such as pulse wave velocity (PWV) and augmentation index (AIx). Methods: Measurements were obtained from 324 patients with newly diagnosed essential hypertension (mean age: 55.0 +/- 8.2 years). The patients were divided into two groups according to their median GGT values. PWV and AIx were calculated using the single-point method via the Mobil-O-Graph (R) ARC-solver algorithm. Results: PWV, Aix, and high-sensitive C-reactive protein (hs-CRP) values were higher and PON1 activity values were lower in GGT(high) group compared with GGT(low) group (P < 0.05, for all). Multiple linear regression analysis showed that GGT activity was independently associated with PWV (beta = 0.496, P < 0.001) and PON1 activity (beta = -0.343, P < 0.001) as well as hs-CRP (beta = 0.334, P < 0.001). Conclusion: These results may support that increased GGT activity would be associated with both impaired antioxidant system and increased AS in hypertensive patients. (C) 2014 Wiley Periodicals, Inc.