Objective LAA anatomy and function have been well characterized both in health and disease state, whereas relatively little attention has focused on the right atrial (RA) appendage (RAA). This study aims to evaluate RAA flow velocity and compare these measurements with left atrial appendage (LAA) indices with biomarker study among patients with sinus rhythm and atrial fibrillation (AF). Methods In a consecutive series of 79 patients referred for transesophageal echocardiography (TEE), 43 patients (23 AF and 20 control ) with 53.9 짹 16.7 years were evaluated and valvular heart disease, malignancy, and severe congestive heart failure were excluded. RAA and LAA flow velocity were measured at multiple orientations (RAA, 90 and 135 degrees; LAA, 0 and 45 degrees). The plasma concentration of brain natriuretic peptide (BNP), C-reactive protein and ESR were measured. Results AF was associated with decrease in flow velocity for both LAA and RAA .(LAA velocity 0.61짹0.22 Vs 0.29짹0.17 cm/sec , p <0.01, RAA velocity 0.46짹0.20 Vs 0.19짹0.08 cm/sec, p< 0.01). Based on simple linear regression analysis , LAA and RAA velocity were positively correlated (r= 0.281, p < 0.01 ). RAA velocity was inversely correlated with BNP. (r=-0.131, p=0.022 ) Conclusion AF is associated with depressed RAA and LAA flow velocities. RAA velocity were found to be positively correlated with LAA velocity and negatively correlated with BNP. The plasma BNP concentration may serve as determinant of LAA function and RAA function. Further study is required to find the clinical significance of RAA.