PIP: The new potential for diagnosing fetal genetic diseases in the first trimester of pregnancy raises the issue of selective abortion in twin pregnancies. If only 1 twin fetus is affected, it is generally necessary to also abort the unaffected twin or to wait until the second trimester and perform selective feticide through use of the air embolism technique. The authors of this paper describe a method that permits selective abortion in multiple pregnancy during the first trimester. An aspirative cannula is introduced through the cervix, guided by ultrasound, and its tip is placed just under the embryo to be aspirated. A 50-ml syringe is linked to the cannula and sudden suction is applied. The embryo is aspirated into the cannula with the amniotic fluid, while the trophoblast is left in place. To date, this method has been applied in 15 cases of multiple pregnancy resulting from ovarian hyperstimulations. It was successful in 12 of these cases. In 2 of the 3 cases where this technique failed, the surrounding trophoblast was also aspirated and spontaneous abortion occurred. Indications for this technique of selective abortion are: 1) pregnancies involving more than 3 fetuses, and 2) an affected cotwin after a positive early prenatal diagnosis.