Reversible aphasia, loss of vision, bradycardia, and mild hypotension occurred in a 6-year-old girl with aplastic anemia and transfusion-related iron overload after inadvertent increase of her intravenous desferrioxamine drip. Signs and symptoms were reversed promptly by intravenous fluids, suggesting that desferrioxamine, when given as a sudden intravenous bolus, may upset vasoregulation. Three possible mechanisms are discussed that could explain this phenomenon. High-dose intravenous desferrioxamine ought to be given by pump infusion only, in order to avoid accidental overdose.