Polycystic ovary syndrome (PCOS) is a common disorder which has considerable phenotypic variability and this has led to controversy over its exact definition and diagnosis. Over the past years a number of definitions have been developed by professional associations. These consensus statements have used a combination of clinical, laboratory and imaging studies as the defining criteria. However, the statements imply that these measures are dichotomous variables without considering factors such as normal physiology, observer subjectivity or measurement variability on the outcome. Published data would suggest that there is considerable uncertainty of all the measurements and that there is a complete lack of clarity of the definition of the term hyperandrogenaemia- and all the factors can lead to misdiagnosis. This paper proposes that the current diagnostic strategies for PCOS are defined too vaguely to be certain that individuals fit the definition of the syndrome. A pragmatic approach may be taken in the management of an individual depending upon her particular symptoms and needs. However, research into the epidemiology, pathophysiology and treatment of PCOS will require the production of robust definitions of the diagnostic criteria.