Context: Women with PCOS are insulin resistant and are at increased risk for sleep apnea, which in turn, may contribute to insulin resistance. Objective: To determine relationships between risk and severity of obstructive sleep apnea (OSA) and glucose metabolism in PCOS. Design and Setting: Two cohorts of women with PCOS in a tertiary care hospital. Patients and Main Outcome Measure(s): Cohort 1 included 40 non-diabetics who completed the Epworth Sleepiness Scale (ESS), the Pittsburgh Sleep Quality (PSQ) and the Berlin Questionnaire (BQ) to assess risk of OSA; 32 of the 40 women had an oral glucose tolerance test (OGTT). Cohort 2 included 8 women who had a sleep study, glycosylated hemoglobin (HbA1C) level and an OGTT. Results: In Cohort 1, 62.5% of the women had poor sleep quality by PSQ Index; 18 (45%) had chronic daytime sleepiness by ESS. Thirty of the 40 women had a high risk of OSA by BQ. Women with high OSA risk had higher fasting insulin levels and HOMA index compared to those with low OSA risk (168.2 ± 17.3 vs 97.2 ± 6.4 pmol/l, p=0.011; 6.3 ± 0.7 vs 3.6 ± 0.3, mg/dl x µU/ml, p=0.014; respectively). Among women with normal glucose tolerance, insulin levels were significantly higher in those at high versus low OSA risk, independently of BMI. Women in Cohort 2 had REM-predominant OSA with lower sleep efficiency, longer sleep latency and less REM sleep than controls. HbA1C levels and the area under the glucose curve positively correlated with the apnea/hypopnea index (r_P=0.82, p=0.013; r_P= 0.96, p=0.0008; respectively) and the number of oxygen desaturations in REM sleep (r_P=0.97, p=0.0009; r_P=0.97, p=0.005; respectively). Conclusion: PCOS is associated with poor sleep quality, daytime sleepiness, and increased risk for OSA. Insulin levels and measures of glucose tolerance in PCOS are strongly correlated with the risk and severity of OSA.