Impaired glucose tolerance (IGT) and Type 2 diabetes mellitus (DM) are common in women with polycystic ovary syndrome (PCOS) in American studies. However, whether rates are similar in other countries with a lower frequency of insulin resistance is not clear. Our purpose was to investigate the prevalence of abnormal glucose metabolism (AGM) in women with PCOS and asses the ability of clinical data and biochemical tests to predict these abnormalities within our population. One hundred and three PCOS women undergo a 75-g oral glucose tolerance test. Glucose tolerance was categorised according to World Health Organisation criteria. Glucose tolerance was abnormal in 18.5% of women: 10.7% had IGT and 7.7% had DM. Women with DM were older than those with IGT or normal glucose tolerance. Women with AGM were more obese, had a higher waist/hip ratio and free testosterone levels than normal glucose metabolism patients. QUICKI was the best predictor of AGM. Receiver operating characteristics analysis suggested a threshold value of 0.31 in quantitative insulin-sensitivity check index (QUICKI) (94.1% sensitivity, 86% specificity, 57.1 positive predictive value and 98.6 negative predictive value) for the prediction of AGM. In conclusion, Mediterranean women with PCOS are at lower risk of AGM than that published from other countries; however, the incidence is still high compared with populations of women without PCOS. We recommend that PCOS patients undergo periodic metabolic screening for AGM using QUICKI.