Magnetic resonance spectroscopy (MRS) has been used for several decades to examine the biochemistry of the myocardium in a non destructive manner. 31P MRS, in particular, has been used to study heart failure. 31P MRS allows for the detection of adenosine triphosphate (ATP), the primary energy source for all energy consuming processes in cardiomyocytes, and phosphocreatine (PCr). Via the creatine kinase (CK) reaction PCr forms the primary ATP buffer in the cell and is involved in transporting the chemical energy from the ATP-producing mitochondria to the ATP-consuming contractile proteins. MRS examination of the failing heart has revealed that PCr, and to a lesser extent, ATP is reduced. These findings have led to the concept that the heart is energy starved. The additional application of 1H MRS has allowed for the detection of total creatine, allowing for in depth examination of the creatine kinase system. Using saturation transfer techniques it is also possible to measure flux through the CK reaction in the intact heart, and the application of this technique has proven that in the failing human heart this flux is reduced. In recent years the study of transgenic animal models by MRS has led to further insights into the role of energy metabolism in heart failure.