Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women and yet remains enigmatic. Despite its high prevalence in the population, much controversy remains regarding its diagnosis, its etiology and the most appropriate treatment strategy. To this end, an international group of scientists meets on a biannual basis to explore this complex disorder, to attempt to derive consensus and to propose areas of importance for research. This year’s meeting was in the U.S. and focused on controversies in PCOS discussed in a debate format. In this edition of Fertility and Sterility, we present four of the discussed controversies. First article: Does PCOS have developmental origins? Drs. Stephen Franks and Sarah Berga discuss key areas of debate regarding the origin/etiology of PCOS. While clearly there is a genetic contribution to PCOS, the role of the intrauterine/post-natal environment and the role of plasticity during development and throughout life, present an interesting juxtaposition for our understanding of PCOS. This section also emphasizes the very nature of PCOS which while including the ovary in the title, represents a disorder involving many organ systems in the body including the brain. Second article: Is PCOS an inflammatory process? Drs. Antoni Duleba and Anuja Dokras present provocative information that not only attempts to explain the association between PCOS and metabolic/cardiovascular risk, but also suggests a etiological source for the hyperandrogenism which is frequently considered a hallmark of the disorder. The controversy continues, however, as the role of PCOS versus the independent role of obesity in the inflammatory process remains unclear. Third article: Do women with PCOS have a unique predisposition to obesity? Drs. Kathleen Hoeger and Sharon Oberfield, present a discussion many of us have had with our patients, all of whom believe this question to be answered affirmatively. But what is the evidence and how do we best counsel our patients with respect to weight loss and any unique predispositions they may have? The correlations between this article and the second article dealing with developmental origins and epigenetic changes supports the complex nature of this question. Fourth article: All women with PCOS should be treated for insulin resistance. While there is evidence of a high prevalence of insulin resistance in women with PCOS, whether this disorder itself requires treatment and, if so, by what mechanism remains controversial. Two experts in the field, Drs. John Marshall and Andrea Duanif discuss this key area in patient management. The negative attitudes about the potential for success with lifestyle interventions frequently support the adoption of medical intervention in the form of insulin sensitizing drugs. This becomes a bit of a philosophical discussion regarding the role of (and support for) lifestyle intervention versus the medicalization of care. This excellent series of articles provides insights into how the experts in the field evaluate PCOS and some key areas ripe for research by both seasoned and young investigators. The Rotterdam criteria remain controversial where an attempt to clarify and standardize the definition of PCOS has actually added to the complexity of this disorder in many ways. These criteria have increased the potential number of phenotypes for PCOS and it is clear that the different phenotypes (including some that have no hyperandrogenism) may have very different etiologies and long-term implications. Given this, it is critical that new literature well-characterize which phenotypes are being studied and how the population was selected. The controversies presented in this issue raise important considerations for future study as well helping to clarify what is currently known and how patients should be approached, evaluated, and treated.