The study was terminated earlier than planned when an interim analysis showed worse outcomes with discontinuation of transfusion therapy. Eight children ( 20%) tolerated removal from long-term transfusion therapy, but there was a high TCD reversion rate and a small risk of stroke despite frequent TCD surveillance.583,584 Further analyses from STOP II also demonstrated increased rates of silent infarcts on MRI in the discontinuation group (27.5% Primary stroke prevention for chil- dren with SCD remains centered on red cell transfusions. Therapies other than transfusion such as hydroxyurea or bone marrow transplantation that reduce the number of pain- ful crises have an uncertain effect on organ damage, including stroke. Of the 127 children with SCD enrolled in the Belgian Hydroxyurea SCD registry, 72 patients were evaluated by TCD. Of these 72, 34 were found at risk of stroke, and only 1 had a cerebrovascular event after a follow-up of 96 patient- years, suggesting a benefit of hydroxyurea in stroke preven- A study of 291 children with SCD included clinical and imaging follow-up of 35 children with abnormal TCDs who were placed on transfusion therapy (median follow- up, 4.4 years). Of 13 patients with normalized velocities on transfusion, 10 had normal MRAs, and transfusion therapy was replaced with hydroxyurea. 