Arterial hypertension (HTN) represents one of the major causes of atrial fibrillation, a cardiac arrhythmia with high prevalence and comorbidity. The aim of this study was to investigate whether paroxysmal atrial fibrillation can be treated by the regression of left ventricular hypertrophy achieved by antihypertensive therapy. Included in the present study were 104 patients who had had HTN for more than 1 year. None of them suffered from coronary heart disease. All patients were investigated by 24-h Holter ECG and echocardiography at baseline and after a mean of 24 months. Patients were divided into two groups: group A consisted of those (53.8%) who showed a regression of the left ventricular muscle mass index (LVMMI) during the follow-up (154.9+/-5.1 vs. 123.5+/-2.8 g/m(2)), and group B those (45.2%) who showed a progression of LVMMI (122.2+/-3.2 vs. 143.2+/-3.2 g/m(2)). In group A the prevalence of atrial fibrillation decreased from 12.5% to 1.8% (p<0.05), while it was increased in group B from 8.5% to 17.0%. The left atrial diameter was reduced following antihypertensive therapy in group A from 39.1+/-5.3 mm to 37.4+/-4.6 mm (p<0.01) and increased in group B from 37.0+/-0.7 mm to 39.0+/-0.9 mm (p<0.01). We conclude that a regression of the left ventricular muscle mass leads to a reduction of left atrial diameter and consecutively to a decrease in the prevalence of intermittent atrial fibrillation. This may be explained by a better left ventricular diastolic function following decreased vascular and extravascular resistance of the coronary arteries. This relation shows the benefits of causal antihypertensive therapy for the treatment of paroxysmal atrial fibrillation.