Two research questions need to be distinguished: research using living tissue from human embryos and fetuses who have been aborted and research on live human embryos and fetuses.

Research using the living tissue from aborted embryos and fetuses for transplant therapy (fetal tissue transplant research) was debated prominently in the early 1990s.

Research on living human embryos was restricted in the 1970s. Over the years efforts were made to loosen these restrictions. In 1996 Congress countered such efforts by passing the Dickey-Wicker Amendment that legislatively banned funding research harmful to the human embryo. Research using living human tissue from living embryos developed a prominence beginning in the later 1990s. This debate evolved as interest focused on taking early embryonic stem cells (pluripotent cells) from living embryos (a process that kills the embryos) and using those cells for research (embryonic stem cell research) or for cloning ("therapeutic cloning"). Also see: Fetal Tissue Research; Human Cloning and Stem Cell Research.