45 pregnant women affected by rhesus incompatibility were treated at the Department of Prenatal Diagnosis and Therapy, Vienna, between January 1992 and March 1993. 32 patients had a cordocentesis and on 21 fetuses, anemia requiring treatment was diagnosed. A total of 71 intravascular transfusions via the umbilical vein was given. The mean number of transfusions per fetus was 3.4 (range 1-11). Of the 7 fetuses who had already developed hydrops when therapy was started (hematocrit < 13%), 5 (71%) survived. The survival rate of non-hydropic anemic fetuses was 93% (13/14). By using intravascular transfusion for treatment of severe fetal anemia, a success rate of 86% (18/21) was achieved.