We describe analyses of the microanatomy of major left ventricular veins, including their relationship to the myocardium. Immediately following fixation of six fresh human hearts, anterior interventricular veins (AIV), left marginal veins (LMV), posterior veins of the left ventricle (PVLV), and posterior interventricular veins (PIV) were sectioned in approximately 5 mm intervals perpendicular to the veins' length from base to apex. Slides were prepared, digitized, and analyzed; measurements were made of each vein's wall thickness, circumference, distance between vein wall and myocardium, and distance between vein wall and closest artery. For analyses, based on the length of each vein, slides were grouped into three regions: basal (top third), mid (middle third), and apical (bottom third). Vein wall thicknesses and circumferences were significantly smaller (P < 0.05) in apical than basal regions in all veins. Vein wall thicknesses were significantly larger in the AIV and PIV than in the LMV and PVLV (P < 0.05). The AIV was significantly farther away (1.81-2.99 mm) from the myocardium than the other three veins (P < 0.05). Left ventricular venous microanatomy was quantified and analyzed. Variation in venous microanatomy, including distance between vein walls and excitable myocardium, could impact therapies involving the coronary venous system. Anat Rec, 2009. (c) 2008 Wiley-Liss, Inc.