Abstract： Background The success and complication rates of atrial fibrillation (AF) ablation may be related to regional differences in left atrial (LA) wall thickness.The purpose of this study was to investigate the transmural LA wall thickness in various regions.Methods We measured LA wall thickness in 36 human heart specimens using calipers at three planes including left pulmonary veins (PVs) vestibule plane,right PVs vestibule plane and the middle plane between the two.In each plane,eight points were selected,including superior,middle and inferior levels at anterior and posterior wall,roof and bottom.Results The anterior and posterior wall thickness displayed gradient from superior to inferior level (anterior wall:(2.73±1.01) mm,(2.08±0.91) mm and (1.54±0.69) mm; posterior wall: (1.74±0.68) mm,(1.48±0.39) mm and (1.27:±0.42)mm).At the roof,LA wall thickness was thickest in middle plane ((2.01±1.02) mm) and was thinnest in left PVs vestibule plane ((1.29±0.41) mm).The posterior wall thickness in left PVs vestibule plane was thinner than in the other two planes (P ＜0.05-0.001),and was thinner in right PVs vestibule plane than in middle plane (P ＜0.01-0.001).Whereas in anterior wall,the wall thickness in left PVs vestibule plane was thicker than in middle and right PVs vestibule plane.Conclusions Significant variations exist for mean LA wall thickness at different regions which are often targeted during circumferential pulmonary venous ablation (CPVA).Appreciating these differences may have significant implications in catheter ablation of AF.