OBJECTIVE: The aim of this study was to evaluate the relationship between adherence to bisphosphonate treatment by postmenopausal women and demographic, health, and lifestyle factors before treatment in a country with universal subsidies for pharmaceutical costs. DESIGN: Older women participating in the Australian Longitudinal Study on Women's Health who consented to linkage to Pharmaceutical Benefits Scheme claims data were included if they filled a bisphosphonate prescription between 2002 and 2005 after a medication-free interval of 180 days (N = 788). A Cox proportional hazards model was used to assess the association of baseline variables with duration of adherence to bisphosphonate treatment. RESULTS: The median time until discontinuation of bisphosphonate treatment was 170 days (95% CI: 154-186). Accounting for socioeconomic status, the baseline variables that were associated with adherence failure were use of acid-related medications (hazard ratio = 1.25, 95% CI: 1.01-1.55) and smoking (hazard ratio = 1.82, 95% CI: 1.26-2.64); reporting high levels of physical activity was associated with better adherence (HR = 0.69, 95% CI: 0.52-0.92). CONCLUSIONS: Overall adherence to bisphosphonate treatment among older Australian women with a fracture history was poor. Inquiring about acid-related disorders and health behavior such as smoking and lack of physical activity could help the prescribing physician to identify women at risk of nonadherence.