The main purpose of this study was to investigate whether in vivo 31P three-dimensional chemical shift imaging (3D-CSI) of the human heart could serve as a useful tool for evaluating myocardial metabolism. We performed slice-selective 3D-CSI employing nuclear magnetic resonance (NMR) imaging with slice selection in one dimension and phase encoding in two dimensions. 31P NMR images of phosphocreatine (PCr) and ATP were superimposed on a corresponding 1H image of the heart. Our study revealed that while accurate in vivo 31P 3D-CSI measurement of the human heart is difficult to achieve it is not impossible, although various additional techniques for improving signal to noise ratio are indicated.