Polycystic ovary syndrome (PCOS) is associated with hyperinsulinemia, insulin resistance (IR), increased risk of glucose intolerance, and type 2 diabetes. Family studies have indicated a genetic susceptibility to PCOS. The aims of this study were 1) to assess glucose tolerance status, gonadotropins, and androgens in first degree relatives of patients with PCOS; and 2) to assess IR in normal glucose tolerant (NGT) family members. One hundred two family members of 52 patients with PCOS [Mothers(PCOS) (n = 34; mean age, 46.5 yr; mean body mass index (BMI), 28.8 kg/m(2)), Fathers(PCOS) (n = 24; mean age, 50.4 yr; mean BMI, 27.5 kg/m(2)), Sisters(PCOS) (n = 19; mean age, 25.1 yr; mean BMI, 22.9 kg/m(2)), and Brothers(PCOS) (n = 25; mean age, 23.7 yr; mean BMI, 22.5 kg/m(2))] and 82 unrelated healthy control subjects without a family history of diabetes or PCOS (4 age- and weight-matched subgroups, i.e. Control(MothersPCOS), Control(FathersPCOS), Control(SistersPCOS), and Control(BrothersPCOS)) were studied. Glucose and insulin (at baseline and during a 75-g, 2-h oral glucose tolerance test) were measured. IR was assessed by fasting insulin (FI), fasting glucose to insulin ratio (FGI), homeostatic model assessment (HOMA IR), and area under the curve for insulin during the oral glucose tolerance test (AUC(insulin)) in NGT Mothers(PCOS), Fathers(PCOS), Sisters(PCOS), Brothers(PCOS), and matched control subgroups. Including the prestudy-diagnosed 3 mothers and 2 fathers with diabetes, diabetes and impaired glucose tolerance (IGT) were noted in 16% and 30% of Mothers(PCOS) and 27% and 31% of Fathers(PCOS), respectively. There was no diabetes in Sisters(PCOS) and Brothers(PCOS). IGT was found in 5% of Sisters(PCOS). Impaired fasting glucose was found in 3% of Mothers(PCOS) and 4% of Brothers(PCOS). The analysis of NGT family members showed that Mothers(PCOS) had higher FI (P < 0.05), HOMA IR (P < 0.05), and AUC(insulin) (P < 0.01) and lower FGI (P < 0.05) than Control(MothersPCOS), whereas all IR parameters were comparable between Fathers(PCOS) and their matched control subgroup. Sisters(PCOS) had higher FI (P < 0.05), HOMA IR (P < 0.01), and AUC(insulin) (P < 0.05) and lower FGI (P < 0.01), and Brothers(PCOS) had higher AUC(insulin) (P < 0.01) than their matched control subgroups, respectively. Mothers(PCOS) had higher testosterone levels than Control(MothersPCOS) (P < 0.01 and P < 0.05 for pre- and postmenopausal women, respectively). Sisters(PCOS) had higher LH (P < 0.01), testosterone (P < 0.001), androstenedione (P < 0.01), and dehydroepiandrosterone sulfate (P < 0.05) levels than Control(SistersPCOS). There was no difference in gonadotropin and androgen levels in Fathers(PCOS) compared with Control(FathersPCOS) or in Brothers(PCOS) compared with Control(BrothersPCOS). Our results suggest that 1) first degree relatives of patients with PCOS may be at high risk for diabetes and glucose intolerance; 2) NGT female family members have insulin resistance; and 3) mothers and sisters of PCOS patients have higher androgen levels than control subjects. We propose that the high risks of these impairments warrant screening in first degree relatives of patients with PCOS.