AIMS To determine whether endogenous oestrogen exposures are associated with open angle glaucoma (OAG). METHODS The Blue Mountains Eye Study examined 2072 women aged 49-97 years during 1992-4. Questions about female reproductive factors included age at menarche and menopause, parity, and use of hormone replacement therapy. Applanation tonometry, visual field tests, and stereo-optic disc photographs were performed. OAG was diagnosed when glaucomatous visual fields matched optic disc changes. Ocular hypertension (OH) was defined in the absence of glaucoma, but with intraocular pressure >or=22 mm Hg. RESULTS A significantly increased OAG risk with later (>13 years) compared with earlier (<or=12 years) age of menarche was found, odds ratio (OR) = 2.0; 95% confidence interval (CI) 1.0 to 3.9, p for trend = 0.01, after adjustment for multiple confounders. Non-significant increased odds for OAG were found for early natural menopause (<45 years) compared with the reference group (>or=50 years), adjusted OR = 1.7; CI: 0.7 to 3.8, and for shorter duration of endogenous oestrogen exposure (<30 years), adjusted OR = 1.8; CI: 0.6 to 5.3. Increasing parity was associated with an increased risk of OAG (p = 0.03) and decreased risk of OH (p = 0.03). CONCLUSION The modest associations found in relation to late menarche and increased parity do not allow the exclusion of a possible role for endogenous female hormones in the pathogenesis of OAG.