B-type natriuretic peptide level is increased in patients with atrial fibrillation. The aim of the present study was to present the distribution of steady-state B-type natriuretic peptide levels of various clinical backgrounds and to elucidate the usefulness of measuring them in patients with atrial fibrillation. B-type natriuretic peptide was measured in stable conditions in patients with atrial fibrillation (74 ± 10 y/o, n = 473). The average B-type natriuretic peptide level was 161 ± 202 (median 101) pg/ml. Multiple regression analysis showed that age, left ventricular ejection fraction, left atrial diameter, structural heart disease, chronic atrial fibrillation, and heart failure symptoms were independently associated with elevated B-type natriuretic peptide levels. However, in chronic atrial fibrillation patients without structural heart disease, B-type natriuretic peptide levels did not differ between those with and without heart failure symptoms. Notably, B-type natriuretic peptide levels were high (≥150 pg/ml) in 41% of asymptomatic chronic atrial fibrillation without structural heart disease. Steady-state B-type natriuretic peptide levels of various clinical backgrounds were presented. Contributions of BNP elevation by clinical variables were somewhat different in different population. B-type natriuretic peptide was elevated in substantial percentage of asymptomatic chronic atrial fibrillation even without structural heart disease.