About 30% of infertility is caused by anovulation, associated most commonly with the polycystic ovary syndrome (PCOS). PCOS is a common endocrinopathy in women, especially at the age of 30 to 35 years, characterized by irregular menses, infertility and signs of hyperandrogenism. The pathogenetic mechanisms leading to PCOS are not fully understood, although several theories have been proposed. PCOS patients commonly have hyperinsulinemia and insulin resistance which are also known risk factors for the development of diabetes mellitus, hypertension and cardiovascular disease. However, it is not known, how well the presence of PCOS symptoms would predict the appearance of the long-term sequelae of insulin resistance. Also more data is needed e.g. of the role of intrauterine factors and birth weight in the development of PCOS and hyperandrogenism.