Desferrioxamine is produced by a type of actinomycetes. It reacts with trivalent iron ions and forms a hydrosoluble complex called ferrioxamine B. This complex is able to remove iron from ferrous protein, but not from hemoglobin. This feature permits its use for the treatment of chronic iron accumulation such as that which occurs in thalassemia. Only two cases of successful desensitization to desferrioxamine hypersensitivity have been previously described. This paper describes a case of desensitization in a six-year-old girl with desferrioxamine hypersensitivity. She suffered from Cooley's disease and had received blood transfusions since the age of three months. From the age of four years, the patient was treated with desferrioxamine, which was interrupted after the occurrence of urticaria-angioedema. Skin and patch tests an in vitro lymphocyte transformation test were negative, indicating a pseudoallergic reaction. The desensitization treatment lasted twenty-one days and, afterwards, the patient was able to tolerate desferrioxamine therapy at the dose previously administered (400 mg/day, subcutaneously).