AIM: To determine whether there are gender differences in the epidemiological profile of atrial fibrillation(AF) and to characterise the clinical, biochemical, and therapeutic factors associated with AF. METHODS: Each investigator (primary care physicians or physicians based in hospital units for hypertension treatment) recruited the first 3 patients with an ageof ≥ 65 years and a clinical diagnosis of hypertension(ambulatory blood pressure monitoring and an electrocardiogram,were performed) on the first working day of the week for 5 wk and identified those individuals with atrial fibrillation. A binary logistic regression was performed, including all of the variables that were significant in the univariate analysis, to establish the variables that were associated with the presence of arrhythmia.CONCLUSION: In patients with hypertension over 65 years of age, there are relevant gender differences in the factors associated with AF.