This chapter mainly focuses on the definition and clinical manifestations of polycystic ovary syndrome (PCOS), its pathogenesis, and the relationship with diabetes and comprehensive care. PCOS is one of the most common endocrine abnormalities in women of reproductive age with a prevalence ranging from 5 to 11%. The most common clinical features of PCOS are irregular cycles, acne, hirsutism, and infertility. The diagnosis of PCOS can only be made when conditions which can mimic PCOS have been excluded like congenital adrenal hyperplasia, Cushing’s syndrome and androgen secreting tumors, hypothyroidism, and hyperprolactinemia. The periodic screening for diabetes and CV risk factors is recommended in all women and adolescents with PCOS with a special focus on prepregnancy counseling. A sustained effort to modify lifestyle to decrease long-term morbidity is to be reiterated at every encounter with the person. Metformin is recommended to be used in patients with PCOS with dysglycemia who have failed lifestyle modifications.