Three-dimensional (3D) endocardial wall motion and thickening were compared as quantitative methods for distinguishing ischemic from non-ischemic myocardium and for their potential to map regional left ventricular (LV) function. Data were obtained by gated magnetic resonance (MR) images in seven open-chest dogs with acute ischemia. The LVs were reconstructed in 3D at end diastole (ED) and end systole (ES) with a helical coordinate system that wraps the endocardium and epicardium. Thickness and percent wall thickening were calculated by a 3D volume element method. Wall motion was calculated by the 3D displacement of the endocardium perpendicular to the wall using both fixed and floating centroids. Monastral blue nonstaining identified the ischemic regions from five anatomical slices of the LV, which corresponded to the in vivo image planes. Thickening and motion were compared at the centers of the ischemic and the remote normal zones, in addition to comparing the functional maps of the entire LV to the postmortem anatomical maps. All methods distinguished between the center of the ischemic zone and the remote normal zone; however, thickening discriminated most strongly between zones. Comparison of the 3D in vivo maps with the 3D postmortem maps showed that the sensitivity, specificity, and overall accuracy of the thickening algorithm exceeded those obtained by the wall motion algorithms with fixed or floating centroids. Thus wall thickening utilizing the 3D volume element approach is superior to 3D wall motion algorithms in distinguishing ischemic from nonischemic zones and in mapping regional function in the entire LV.