This observation reports a case of superfetation which occurred in connection with gamete intrafallopian transfer (GIFT). The macroscopic and histological examination of a spontaneous abortion from a 33-yearold woman (15th week of pregnancy) revealed the existence of two embryos with a monochorionic diamniotic placenta (developmental age approximately 41 days) and two fetuses and a fetal remnant with a trichorionic and triamniotic placenta (developmental age approximately 98 days). The large developmental age difference of embryos and fetuses cannot be explained by retardation, because the embryos showed adequate development with the development of their placenta. Moreover, the usual causes of intrauterine growth retardation could be excluded as could retention of the embryos since the tissues showed no autolytic changes. Consequently the large developmental age difference is explained by assuming that the embryos developed from successive ovulations. A second nidation of blastocysts had occurred after the GIFT concurrently with the clinically reported hyperstimulation syndrome.