The ethical attitudes of health care providers toward abortion, sex selection, and selective termination of normal and anomalous fetuses in singleton or multiple pregnancies were evaluated by questionnaires distributed to members of the American Society of Human Genetics, the International Fetal Medicine and Surgery Society, the Society of Perinatal Obstetricians, ethicists, and clergy. Demographic characteristics of respondents exhibited a preponderance of men (76%), age > 40 (68%), and of United States residents (82%). Seventy-nine percent of respondents were in the medical profession. Approximately half of the respondents were Protestant, the rest being evenly distributed among Catholic, Jewish, and other religions. Acceptance of abortion for social indication varied by religion and gestational age but not by religious conviction, age, country, or gender of respondent. First-trimester abortion of a normal singleton pregnancy was considered more acceptable than selective termination of normal fetuses in multifetal gestations. Sex selection was considered unethical by most respondents. Selective termination was deemed ethically appropriate in quadruplets or multifetal gestations of more than five fetuses and in multiple pregnancies bearing one anomalous fetus. In the latter situation, acceptance increased with the severity of fetal anomalies and decreased from the first to the third trimester. The medical specialty of respondents was the only independent factor strongly associated with acceptance of selective termination by trimester, indication, and number of fetuses. Acceptance of selective termination among health care professionals appears to reflect not only perceptions of procedure-related risks and benefits in the index pregnancy but also individual training and religious beliefs.