Objectives: To determine whether statin treatment is associated with increased risk of haemorrhagic stroke (HS) in older women. A secondary objective was to evaluate HS risk in users of combined statin and antiplatelet treatment. Design: Observational study: secondary data analysis from the Women's Health Initiative (WHI) clinical trials. Setting: Women were recruited from 40 participating sites. Participants: Cohort of 68 132 women followed through 2005 (parent study) and for an additional 5 years in the extension study. Main outcome measures: Statin use was assessed at baseline and at follow-up visits (1, 3, 6 and 9 years). Women brought medications in original containers for inventory. Strokes were ascertained semiannually and centrally adjudicated. Risk of HS by statin use (timevarying covariate, with the 'no use' category as the referent) was estimated from Cox proportional hazard regression models adjusted for age (model 1); risk factors for HS (model 2); and possible confounders by indication (model 3). Prespecified subgroup analyses were conducted by use of antiplatelet medications. Results: Final models included 67 882 women (mean age, 63±7 years). Over a mean follow-up of 12 years, incidence rates of HS were 6.4/10 000 person-years among statin users and 5.0/10 000 person-years among non-users (p=0.11). The unadjusted risk of HS in statin users was 1.21 (CI 0.96 to 1.53); after adjusting for age and HS risk factors the HR was 0.98 (CI 0.76 to 1.26). Risk of HS was higher among women on statins and antiplatelet agents versus women on antiplatelet medications alone (HR=1.59; CI 1.03 to 2.47); p for interaction=0.011. Conclusions: This retrospective analysis did not show an association between statin use and HS risk among older women. HS risk was higher among women taking statins with antiplatelet agents. These findings warrant further investigation, given potential implications for clinical decision-making.