The number of multifetal pregnancies has increased dramatically as a result of the widespread clinical use of ovulation induction and assisted reproductive technology(ART) in infertile patients. In multifetal pregnancies, the adverse outcome is directly proportional to the number of fetuses within the uterus, primarily because of an increased predisposition to premature delivery. It is extremely difficult to counsel patients about the expected outcome of pregnancies involving three or more fetuses. To increase the chances of delivering infants mature enough to survive without being irreversibly damaged by the sequelae of marked prematurity, selective fetal reduction(SFR) to the smaller number of fetuses should be considered in multifetal pregnancies. From January, 1991 to December, 1992, transabdominal SFR in multifetal pregnancies was performed in 22 patients including 13 triplet, 7 quadruplet, 1 quintuplet and 1 heptuplet pregnancies. Transabdominal SFR using intracardiac KCI injection and aspiration of amniotic fluid was carried out in 8-13 weeks of gestation. After procedure, 20 patients were remained as twin pregnancies, and 2 patients as triplet pregnancies. There have been 11 sets of twin delivery including 2 stillbirths, 2 sets of triplet delivery including 1 stillbirth, and 1 singleton delivery. Six cases were delivered after 37 weeks of gestation, 4 cases in 33 - 37 weeks, and 1 case in 30 weeks. Unfortunately, 3 stillbirths occurred in 20-24 weeks of gestation, and 4 cases were aborted. As 7 losses of pregnanancy including 1 case of septic abortion occurred, the delayed fetal loss rate was 38.9%(7/18) in transabdominal SFR. All babies born after 30 weeks of gestation were healthy, and no fetal anomaly directly related to the procedure was encountered. From July, 1993 to February, 1995, transvaginal SFR was performed in 20 patients including 15 triplet, 4 quadruplet and 1 quintuplet pregnancies. Transvaginal SFR using the same method as transabdominal SFR was carried out in 8-11 weeks of gestation. After procedure, 19 patients were remained as twin pregnancies, and 1 patient as singleton pregnancy. There have been 13 sets of twin delivery including 2 stillbirths, and 1 singleton delivery. Six cases were delivered after 37 weeks of gestation, 5 cases in 36-37 weeks, and 1 case in 30 weeks. Unfortunately, 2 still-births occurred in 20 weeks and 21 weeks of gestation, respectively, and 2 cases were aborted. As 4 losses of pregnancy including 1 case of septic abortion occurred, the delayed fetal loss rate was 25.0%(4/16) in transvaginal SFR. No fetal anomaly directly related to the procedure was encountered. It is suggested that transvaginal SFR could be performed more easily and earlier with the lower fetal loss rate as compared with transabdominal SFR. In conclusion, SFR is a rather safe and ethically justified procedure that may improve the outcome of multifetal pregnancies.