Quantitative measurements of hepatic and cardiac iron by single-breath-hold MRI T2* will allow us to determine the value of this technique as a non-invasive method of monitoring liver and cardiac iron content. By obtaining T2 measurements, we will be able to compare two different techniques for non-invasive iron assessment. With regard to the liver, we will correlate T2* measurements with the gold standard, LIC on liver biopsy. Because it is not feasible to perform cardiac biopsies to evaluate the degree of cardiac hemosiderosis, we will evaluate the relationships between cardiac T2* values and left and right diastolic function, left ventricular ejection fraction, left ventricular end-systolic volume and left ventricular mass index obtained by echocardiography and MUGA scans that are performed as part of the routine clinical care of these patients. In order to estimate whether cardiac T2* values are clinically relevant, we will also investigate the relationship between T2* values and the need for cardiac medication due to cardiac hemosiderosis. Cardiac and hepatic T2* measurements will also be compared to their visual appearances on T2* MR images in order to investigate the relationship between these two assessments. Cardiac and hepatic T2* and their respective visual appearances on T2* MR images will be compared with serum ferritin to evaluate the potential relationships among these measurements of iron overload.