Polycystic ovary syndrome (PCOS) is associated with increased risk of impaired glucose tolerance and type 2 diabetes. PCOS has been considered as a major risk factor for the development of diabetes, and screening of women with PCOS for glucose intolerance is suggested. Detection of glucose intolerance in PCOS is best performed via 2-h oral glucose tolerance test rather than fasting plasma glucose alone, since it enables diagnosis of both impaired glucose tolerance and diabetes. Insulin resistance is a prominent feature of PCOS, although not all women with PCOS have insulin resistance. Measurement of insulin resistance is not included in the diagnostic criteria of the syndrome, and not required for the selection of treatments in current clinical practice. However, this measurement is undoubtedly of interest for clinical research studies of PCOS. Several methods are available to the clinical investigator for the measurement of insulin resistance, yet there is no universally accepted and clinically useful definition, and no specific guidelines about how to measure it. While hyperinsulinaemic glucose clamp is considered to be the 'gold standard' for the measurement of insulin resistance, several alternative methods have been validated against the cold standard. Each method has its own merits and disadvantages. The choice of method for a particular study should be based on the specific aims, size, and type of that study. Variability in measurement of insulin resistance due to physiological factors, assay-related problems, and protocol differences in dynamic function tests deserves Much more emphasis when interpreting the results of a study. or making comparisons between studies.