Intrauterine intravascular transfusion for the treatment of severe erythroblastosis fetalis has resulted in a number of benefits: (a) Direct access to the fetal vasculature allows an accurate assessment and prompt correction of anemia, albeit temporary. In contrast, intraperitoneally transfused blood may be absorbed erratically, especially in the face of ascites. (b) Intravascular treatments can be performed, in general, as early as 17 weeks of gestation, earlier than intraperitoneal approaches permit. (c) Reversal of hydrops along with the correction of anemia and hypoproteinemia has significantly reduced neonatal morbidity and mortality. None of the surviving neonates in our series required either thoracentesis or paracentesis following delivery, and 40% did not require neonatal exchange transfusion. (d) Treatments may be safely performed until pulmonic maturity has been established and/or an EFW of greater than 2,000 g has been reached, reducing problems of prematurity. (e) Central vein and umbilical vein hypertension may be arrested or prevented, thereby allowing fetal liver function to return to normal. While isoimmunization stands as a disease that has been quite successfully reduced in frequency and severity by the careful attention and treatment by obstetricians, cases still occur. Due to the reduced frequency of severe disease, fewer physicians are trained and experienced in performing this difficult procedure. As fewer transfusions are required, the value of regionalized treatment centers will have to be considered carefully, in order to maximize the experience and efficiency of the intravascular intrauterine transfusion treatment teams.