OBJECTIVE We evaluated menopausal symptoms, menstrual cycle bleeding characteristics and reproductive hormones for their associations with thyroid stimulating hormone (TSH) concentrations in women at the mid-life from five ethnic groups. METHODS This report is from the baseline evaluation of the Study of Women's Health Across the Nation (SWAN), a community-based multiethnic study of the natural history of the menopausal transition. Enrollees were 42-52 years old (pre- and early perimenopausal) African American, Caucasian, Chinese, Hispanic and Japanese women (n = 3242). Enrollees were interviewed about self-reported diagnosed hypo- and hyperthyroidism or thyroid treatment, menopausal symptoms and menstrual cycle bleeding characteristics. Serum was assayed for TSH, oestradiol, testosterone, FSH and SHBG. RESULTS There were 6.2% of women with TSH > 5.0 mIU/ml and 3.2% with TSH 5.0 mIU/ml (P < 0.008) or < 0.5 mIU/ml (P < 0.02). Women with TSH values outside the range of 0.5-5.0 mIU/ml were more likely to report shorter or longer menstrual periods (P = 0.004 for both) than women within that range. FSH, SHBG, dehydroepiandrosterone sulphate (DHEA-S), testosterone, and oestradiol concentrations were not associated with TSH concentrations. CONCLUSION In mid-aged women, there was a 9.6% prevalence of TSH values outside the euthyroid range of 0.5-5.0 mIU/ml. Although TSH was associated with bleeding length and self-reported fearfulness, it was not associated with indicators of the menopausal transition, including menopausal stage defined by bleeding regularity, menopausal symptoms or reproductive hormone concentrations.