AIMS: To compare different methods in order to assess adherence and persistence with oral endocrine therapy in women diagnosed with breast cancer (BC) in Catalonia. MATERIALS AND METHODS: This study covered all women newly diagnosed with stage I, II or IIIa BC and positive hormone receptors at six hospitals in Catalonia (Spain) in 2004. Adherence was assessed on the basis of physician report and patient self-report using a telephone questionnaire. Persistence was measured by refill prescriptions. We used the Kappa index to compare adherence measures and logistic regression to evaluate adherence-related risk factors. RESULTS: The study covered a total of 692 women. Adherence ranged from 92% (self-report) to 94.7% (physician report), depending on the measure used; persistence was 74.7% at 5 years of follow-up. Low concordance between measures was observed (Kappa range: 0.018-0.267). Patients aged 50-74 years showed higher adherence than those aged <50 years. Adherence was also associated with: adjuvant chemotherapy and sequential hormonal therapy. CONCLUSIONS: Concordance between the different measures was remarkably low, indicating the need for further research. Adherence is an issue in the management of BC patients taking oral drugs, and should be assessed in clinical practice.