Aim: assessment effect of myoinositol on insulin resistance in women with poly cystic ovarian syndrome. Drawings: the diagnosis of PCOS was based on the Rotterdam criteria, which necessitated 2 of the following 3 features: 1. oligoovulation and anovulation (less than 6 times in 12 months) 2. Clinical or biochemical signs of hyperandrogenism such as acnea, allopecia or high androgen level 3. Polycystic ovaries on ultrasound examination. Design: The questionnaires were included height, weight, body mass index, waist, menstruation pattern, infertility, fasting glucose, fasting insulin, insulin resistance index, low density lipoprotein, high density lipoprotein, triglyceride, dehydroepiandastione, free testosterone were measured in these patients. Inclusion criteria: women who were between 20 and 40 years old, and had PCOS diagnosed by a gynecologist. Exclusion criteria: patients who were diagnosed with Cushing syndrome, congenital adrenal hyperplasia, hyperprolactinemia, hypothyroidism, hyperthyroidism, andogen secreting tumor, medications known to affect metabolic parameters, such as metformin and corticosteroid drugs, vitamin D, and serum calcium. Intervention: the patients received myoinositol 4 grams daily for 3 months and the pilot checked again three months after treatment. Written consent form was obtained from all patients. Primary outcome measure: fasting glucose, fasting insulin, HOMA IR. Secondary outcome measure: height, weight, body mass index, low density lipoprotein, high density lipoprotein, free testosterone, dehydoeoiandrastione, triglyceride.