Patients with sickle cell anemia often require blood transfusion as part of the treatment for their disease. Each teaspoon of transfused blood contains about 5 mg of iron and the levels of iron in sickle cell patients increase rapidly with each transfusion. While iron is necessary for many bodily functions, too much iron damages blood vessels, liver, hormone producing glands (pancreas, pituitary and thyroid) and the heart. It is important to know how iron damages blood vessels because most of the problems experienced by sickle cell anemia patients (stroke, kidney failure, pulmonary hypertension, heart disease) result from blood vessel damage. In this trial, iron in the liver, pancreas, and kidney will be measured noninvasively by MRI while vascular function will be measured by ultrasound and tissue Doppler. Patients will be recruited primarily from the greater Los Angeles area, although patients from greater distances will be allowed to participate.