To investigate changes in glycemic status in women with polycystic ovary syndrome (PCOS) DESIGN: Longitudinal observational study PATIENTS: Women with PCOS who underwent baseline and follow-up screening tests for diabetes (n=262). Four patients with type 2 diabetes (T2DM) at baseline and 6 patients who were taking drugs at the final follow-up were excluded.Changes in glycemic classification based on fasting glucose, hemoglobin A1c and oral glucose tolerance test.The median length of follow-up was 2.9 years. The mean age and body mass index in the normoglycemia group (n = 202) was 23.0 years and 21.6 kg/m2 , while it was 23.6 years and 22.9 kg/m2 in the prediabetes group (n = 50). In the normoglycemia group, 38 (18.8%) and 2 (1.0%) developed prediabetes and T2DM, respectively. In the prediabetes group, 22 (44.0%) remained in the same category, 6 (12.0%) developed T2DM, while 22 (44.0%) achieved normoglycemia. The incidence rate of T2DM was 9.3 per 1,000 person-years, which was significantly higher than that of the female population of similar age, and the incidence was higher in women with fasting glucose ≥ 5.6 mmol/L at baseline than in women with < 5.6 mmol/L.About 20% of normoglycemic women had developed prediabetes or T2DM after a median time of 2.9 years. Meanwhile, nearly half of prediabetes women achieved normoglycemia. Higher baseline fasting glucose levels were associated with an increased incidence of T2DM. Our results are the first to evaluate glycemic status changes using all three parameters in PCOS patients.