Objective: Polycystic ovary syndrome (PCOS) is a common endocrine disorder in women of reproductive age. The renal resistive index (RRI) is a measure of renal arterial resistance to blood flow. The aim of this study was to investigate the renal resistive index levels of patients with PCOS. Subjects and methods: A total of 216 women were included in this cross-sectional study.The study group consisted of 109 patients with PCOS, and the control group consisted of 107 healthy subjects. The RRI of all subjects was measured using renal Doppler ultrasonography. Results: The patients with PCOS had higher RRI levels in comparison to the healthy subjects (0.64 +/- 0.06 vs. 0.57 +/- 0.06, p < 0.001).The RRI levels of the patients with PCOS were correlated with systolic blood pressure (p = 0.004, r = 0.268) and with homeostasis model assessment of insulin resistance (HOMA-IR) (p = 0.02, r = 0.216). Conclusion: In this study, we observed higher RRI levels in patients with PCOS. High RRI levels may be an indicator of cardiovascular and/or cardiovascular-associated diseases in patients with PCOS.