Polycystic ovarian syndrome (PCOS) is a reproductive system disorder characterized by irregular menses, anovulation,clinical and/or biochemical signs of hyperandrogenism (hirsutism and/or acne), ovarian micropolycystic appearance andmetabolic abnormalities, such as hyperinsulinaemia and obesity. The aetiopathogenesis of this syndrome is not well known.Several pathogenetic hypotheses have been proposed to explain the full array of symptoms and signs, but with elusiveresults. A genetic abnormality causing PCOS is supported by the observation that different members of the same family areoften affected, and about half of the sisters of PCOS women have elevated serum testosterone concentrations. Therefore, thepresence of gene abnormalities in women with PCOS has been widely explored in the attempt to establish whether theirmutations or polymorphisms may cause PCOS. The main genes evaluated are those involved in steroidogenesis, steroidhormone effects, gonadotrophin release regulation and action, insulin secretion and action, and adipose tissue metabolism.Despite the vast body of literature produced, none of the genes evaluated seems to play a key role in PCOS pathogenesis.It is likely that PCOS may represent the final outcome of different, deeply inter-related genetic abnormalities that influenceeach other and perpetuate the syndrome.