Background and Objectives: Renin-angiotensin system (RAS) inhibitors are likely to reduce the development of atrial fibrillation (AF) by preventing atrial fibrosis. Strain imaging is a novel echocardiographic technique to quantify left atrial (LA) function. We attempted to assess the relevance of strain echocardiography for quantitative assessment of the LA status in AF, its modification by RAS inhibitors and changes of biochemical markers during cardiac remodeling in AF. Subjects and Methods: Strain echocardiography (Vivid 7, GE) is performed 2 times (baseline and 12 month) in 60 patients with AF (RAS inhibitors- used group: 30, non-used group: 30) and 30 controls. In an apical 4-chamber view, the regional analysis consisted of placing the region of interest cursor at the basal segments of the septal (sia) and lateral wall of LA. Mean peak systolic and peak early diastolic strain are measured with LA end-systolic antero-posterior, longitudinal and transverse dimensions. Results: 6 patients of RAS inhibitors- used group (20%) and 3 patients of non-used group (10%) were converted to normal sinus rhythm during the study. LA size, E wave velocity, E/E���, peak systolic and diastolic strain showed no significant differences between groups at the baseline. There were no significant differences in LA size and E wave velocity between groups at the 12 months, however, peak systolic and diastolic strain were significantly higher in RAS inhibitors- used group (36.71짹 13.63%, -2.69짹3.30%, p<0.05, respectively) than non-used group (27.21짹10.49%, -0.83짹2.79%, respectively). There were no significant differences in CRP and BNP at the baseline, but BNP were significantly reduced in RAS inhibitors- used group (822.9짹798.3 pg/ml, p<0.05) than non-used group (1481.9짹 209.97pg/ml) at the 12 month. Conclusion: The increased values of atrial peak systolic and diastolic strain after treatment with RAS inhibitors revealed that passive stretching and shortening of LA wall may improve in some patients with AF even before LA size change possibly because of reduced atrial fibrosis and increased compliance. Our results indicated that strain echocardiography provide clinically useful information of LA function and remodeling.