Stroke is among the most complication of sickle cell disease (SCD). It occurs in 6 to 9% of Hb SS patients, affecting all age groups almost equally except for those less than 1 year of age in whom the incidence is much lower. The most common cause of stroke in children with SCD is thrombotic infarcts due to cerebrovascular disease. In addition to stroke, there is mounting evidence that SCD is associated with neuropsychological dysfunction the cause of which may also be due to cerebrovascular disease. Patients who develop stroke are clinically and hematologically indistinguishable from those who do not. While several neuroradiological and other techniques are employed to study the brain after the occurrence of stroke, there are no measures routinely applied to try to determine which patients may be at the risk for stroke. Some of these methods are not suitable for routine and repeated application in clinically asymptomatic patients for various reasons. The availability of magnetic resonance (MR) technology is making the detection of cerebral pathology before a clinical neurologic event, possible. MR imaging (MRI) has revealed clinically silent infarction over 10% of patients studies so far. The Cooperative Study of Sickle Cell Disease is currently conducting brain MRI and psychometric studies in children over 6 years of age. We and others have been employing MRI, MR angiography (MRA), and MR spectroscopy (MRS) to study cerebral pathology in sickle cell patients. Data from over series of stroke patients suggest that the neurological consequences of stroke may be more devastating in children less than 5 years of age. The overall objective of our proposed study is to employ non-invasive MR methods serially to study the brain of young children with SCD in order to detect and monitor cerebral pathology. We propose to recruit cohorts of one and two-year old patients who will undergo MRI, MRA, and MRS yearly for 5 years. Concurrent with the MR studies, they will also undergo neuropsychological testing. We will compare the results of these studies with normative data, and try to correlated abnormal finding on MR studies with the findings on neuropsychological tests. Patients who develop new strokes will also be evaluated with the same methods in order to determine whether the methods may be useful in predicting outcome of stroke.