Polycystic ovarian syndrome (PCOS), includes a wide spectrum of clinical symptoms and signs. Three different diagnostic classifications have been proposed to define this disease. The first one, published in 1990, known as the "NIH criteria" requires the simultaneous presence of hyperandrogenism and menstrual dysfunction in order to diagnose PCOS. Later on, in 2004, an expert panel met in Rotterdam and added to the previous criteria the presence ofpolycystic ovarian morphology (PCOM) detected by transvaginal ultrasonography The later classification broadened the spectrum of PCOS and also included women with oligomenorrhea and PCOM without hyperandrogenism or hyperandrogenism and PCOM without menstrual dysfunction. Finally, the Androgen Excess Society, published in 2006 new diagnostic criteria which required the presence of clinical or biochemical hyperandrogenism, with either PCOM or menstrual dysfunction to diagnose PCOS. We review the different classifications employed in the diagnosis of PCOS, the diverse phenotypes that may lead to the diagnosis of PCOS and their association with cardiovascular and metabolic complications.