Hemochromatosis is a hereditary iron overload syndrome characterized by increased iron storage, followed by liver cirrhosis and is often associated with restrictive cardiomyopathy. The purpose of this study was to detect alterations of cardiac high-energy phosphate metabolism in patients with hereditary hemochromatosis (HHC) prior to the development of structural heart diseases. Therefore cardiac phosphorus-31 two-dimensional chemical shift imaging ( 31 P 2D CSI) was employed. Twenty-four male patients (mean age 47.2 ฯฎ 12 years) homozygous for the C282Y mutation in the hemochromatosis associated HFE gene and twentyfour male healthy volunteers (mean age 47 ฯฎ 11 years) as age-matched controls were included in this study. Using a 1.5-Tesla whole-body magnetic resonance scanner, electrocardiographtriggered transversal 31P 2D CSI was performed. Left ventricle mean phosphocreatine (PCr) to โค-adenosine triphosphate (โค-ATP) ratios of patients with HHC (1.60 ฯฎ 0.41) were significantly decreased in comparison to healthy volunteers (1.93 ฯฎ 0.36; p ฯญ 0.004). Furthermore, we detected moderate, negative correlations between left ventricular PCr to โค-ATP ratios and transferrin saturation, cholesterol, low-density lipoprotein as well as triglyceride. This study shows that 31P 2D CSI permits the detection of alterations of cardiac high-energy phosphate metabolism in patients with HHC, but without any evidence for heart disease. The decreased PCr to โค-ATP ratios in HHC might be caused by mitochondrial impairment due to cardiac iron overload.