Thirty-seven fetuses with severe rhesus isoimmunization with a gestational age of less than 30 week underwent 92 intravascular transfusions. Of these, 77 were intracardiac, 13 umbilical vein and two umbilical artery transfusions. Procedure related complications occurred at eight (10%) intracardiac and at two (14%) umbilical cord transfusions. Reversal of hydrops was observed in 10 of 16 fetuses. The perinatal mortality among transfusion treated fetuses was 8/37 (21%). It is concluded that intravascular, intrauterine transfusion leads to improved results among fetuses with early onset of hydrops. Problems concerning indications and technique are discussed.