Study aim: The aim of this study is to determine the effects of zinc supplementation on nitric oxide and biomarkers of oxidative stress in women with polycystic ovary syndrome (PCOS). Design: Study design: Parallel double-blind (both patients and researchers) randomized controlled clinical trial. Random assignment will be done by the use of computer-generated random numbers. Settings and conduct: Population and sample size: 48 women with PCOS eligible and referred to Kosar outpatient Clinic affiliated to Arak University of Medical Sciences, Arak, Iran in the study will be selected. Participants/Inclusion and exclusion criteria: Inclusion criteria: Patients with polycystic ovary syndrome and aged 18 to 40 years will be included in this study. Exclusion criteria: Hyperprolactinemia, thyroid disorders, liver or kidney diseases, pregnancy and lactation, the use of medications such as insulin sensitizers, insulin, and diuretics, subjects following a special diet or consuming drugs with an effect on hormonal profile like oral conceptives (OCP), steroid hormones, or any other drugs probably to affect ovarian action in the last 3 months, T2DM Intervention groups: Intervention: Patients will be assigned to receive either 50 mg zinc supplement (intervention group: n=24) or placebo (control group: n=24). Fasting blood samples will be taken at baseline and after 8-wk intervention to measure nitric oxide and biomarkers of oxidative stress. Start and End Date of Intervention: 8 weeks Main outcome variables: Outcomes: Free testosterone, dehydroepiandrosterone (DHEA), alopecia and hirsutism (primary outcome), and other hormonal profiles, biomarkers of inflammation and oxidative stress (secondry outcomes) will be quantified at the study baseline and end-of-trial.