Successful intrauterine transfusion of the fetus with erythroblastosis fetalis has been reported by Liley (1) and McCrostie (2). The purpose of this paper is to familiarize the radiologist with the technic involved in performing the procedure. Hematology Intrauterine intraperitoneal transfusion can be of value to a limited number of fetuses which are not hydropic at twenty-six weeks gestation, but are expected to be severely affected by thirty-four weeks. Establishing the severity of the erythroblastotic process in a fetus is possible not only by measurement of the rising maternal antibody, but also by spectrophotometric analysis of amniotic fluid. In the face of expected severe erythroblastosis, red cells have been infused into the peritoneal cavity of the fetus (1, 2). Absorption of intact red cells from the peritoneal cavity has been well established by Mellish and Wolman (3). It is unlikely that the technic to be described can be adapted to fetuses smaller than those of twenty-six weeks gestation. Technic Thirteen intrauterine fetal infusions have been performed in the Department of Radiology, Boston City Hospital. The patient is premedicated with morphine sulfate (20 mg) and phenobarbital (100 mg). Preliminary films are not necessary, as on two occasions movement of the fetus was found to invalidate the position described on radiography. With the patient supine, the abdomen is viewed with television monitoring for delineation of the fetus. It should be stressed that sharpness is needed; therefore, prior to exposure of the fetus, we have used a pelvic phantom for quality control check of the television image (see below.) The abdomen is then prepared and draped, and the site of injection in the abdominal wall is anesthetized with 1 per cent Xylocaine. An 8-in. No. 16 Tuohy needle is introduced into the amniotic sac at a point approximating the anterior abdominal wall of the fetus. After its position is checked by television monitoring, the needle is inserted into the peritoneal cavity of the fetus. We attempt to approximate the low fetal abdomen with caudad angulation of the needle to avoid liver or kidney puncture. When the needle enters the peritoneal cavity, and the stylet is withdrawn, one can frequently hear a characteristic “whistle.” Five cc of methylglucamine diatrizoate6 is injected to check the needle position. If its end is free, the opaque medium will outline the diaphragm, giving a crescent shape which is easily visualized fluoroscopically (Fig. 1). Occasionally, the injected opaque medium puddles in the low or mid abdomen. In this situation, contrasted bowel loops of the fetus may be seen, indicating the intraperitoneal location of the needle tip. Once the needle end is free, 50 to 100 cc of packed red cells are injected into the peritoneal cavity of the fetus. An anteroposterior or lateral exposure was at one time obtained at the termination of the procedure as a record of the location of the medium.