During the past 40 years, rhesus alloimmunization has gone from being one of the major causes of perinatal mortality to an almost eradicated disease. The unraveling of the pathophysiology, the development of reliable diagnostic tools, a very effective prophylaxis program, and for those (nowadays rare) cases slipping through the prevention system the availability of treatment by intrauterine blood transfusions, together constitute one of the great triumphs in modern medicine. Although Rh-D alloimmunization remains the most common indication for fetal blood transfusion therapy, an increasing percentage of these procedures is used to treat other causes of fetal anemia such as Kell alloimmunization and parvovirus B19 infection. Apart from transfusing blood, the same technique can be used to transfuse platelets to thrombocytopenic fetuses. This chapter describes the technique of fetal transfusion, and reviews the current management of fetal anemia and fetal thrombocytopenia.