First described in 1935, polycystic ovary syndrome (PCOS) is a frequent endocrine disease (6% in female population). However its pathogenicity is not yet completely understood. The possible etio-pathogenic mechanisms include: neuroendocrine disorders (hypothalamic, as a result of congenital androgenism or of disorders of neurotransmitters or pituitary, with excess of LH), ovarian disorders (enhanced sensibility at LH, local growth factors, hyperactivity of Cit P450cl7 alpha enzymes), adrenal disorders, insulin resistance, genetic determinism, puberty onset. The authors discuss in detail this hypothesis and these possible importance.