Since the identification of Thalidomide as a potent human teratogen, the possible effects of a large number of drugs, and chemical, physical and environmental agents, on the embryo and the fetus have been raised without support of scientific demonstration. During the last ten years, a large number of papers were published on this issue, making the understanding of teratogenic mechanisms and effects a new field for investigation. This review is to show the recent trends and concepts on human teratogenesis induced by extrinsic agents, making it clear that the majority of them can not be seen as harmful to humans.