Cardiac magnetic resonance (CMR) has gained increasing clinical application in cardiopulmonary diseases. Due to its 3-dimensional nature, CMR is considered the gold-standard for quantifying left and right ventricular systolic function and size. Additionally, its high tissue contrast allows for a detailed characterization of myocardial tissue. Specifically, the use of techniques such as late gadolinium enhancement can be used to detect the presence of tiny amounts of myocardial scar. Other techniques have been shown to correlate strongly with myocardial iron content. Just as importantly, CMR perfusion imaging can accurately quantify myocardial blood flow and can provide tremendous insight into the function of the microcirculation. CMR's high spatial and temporal resolution, its 3-dimensional approach, its ability to characterize the tissue, and its ability to evaluate the micro- and macro-circulation make it a comprehensive technique for the evaluation of heart disease. Recently, one CMR study has already shown the presence of cardiac microvascular disease in a subset of adult sickle cell disease (SCD) patients in the absence of infarcted myocardium, myocardial iron overload, or coronary artery disease, increasing the evidence for the contribution of left heart disease to pulmonary hypertension (PH) development in these patients; unfortunately, strong conclusions could not be made because the study was underpowered. Thus, this proposal will leverage the advantages offered by CMR to better characterize and detect the PH and cardiopulmonary subphenotypes in the SCD patient population.