We report herein a technique for direct intraendometrial transfer (DIET) of human embryos. In this study we evaluated whether 2-day embryos injected into the endometrial stroma can develop normally into viable pregnancies. After in vitro fertilization the embryos were injected into the endometrium of 14 women under direct visualization using a CO2-pulsed flexible hysteroscope. A total of 44 embryos were transferred, resulting in 2 clinical (14.3% per cycle) and 2 chemical pregnancies. In 1 patient, amniocentesis revealed monosomy X and the pregnancy was terminated at 18 weeks. The 2nd patient had an uneventful pregnancy and delivered a healthy baby. The results from the present study, demonstrating a low implantation rate after DIET of 2-day embryos, suggest that the endometrial stroma does not provide an optimal environment for early embryonic development. The acidifying effect of CO2 used for insufflation may also explain the low pregnancy rate after DIET. We conclude that it is possible to achieve pregnancy by DIET in humans, but presently this procedure can be considered only in cases where the implantation site needs to be precisely determined.