The purpose of this study was to investigate whether the ideal control of atrial fibrillation (AF) associated with hypertensive patients depends on the usage of renin-angiotensin system (RAS) inhibitors or whether it occurs regardless of the kind of antihypertensive agents used. The control of AF was compared in 112 outpatients between 1) those with or without the administration of RAS inhibitors, and 2) those with an ideal or poor control of the blood pressure (BP) regardless of the kind of antihypertensive therapy used. The therapies with or without RAS inhibitors did not yield any significant difference in the AF control states, even though RAS inhibitors had been administered to the patient group with a high proportion of organic heart disease. The ideal BP control group exhibited a significantly better AF control in comparison to the poor BP control group. The former group had a significantly smaller left atrial diameter determined by ultrasonic echocardiography. BP control itself may essentially be important for preventing AF in the general patient population. Poor BP control seemed to have an affect on worsening AF possibly via left ventricular diastolic dysfunction, followed by left atrial overload.