Since the inception of in vitro fertilization (IVF), the procedure has seen many advances that have significantly improved pregnancy RATEs as well as a reduction in complication RATEs.The benefits of blastocyst stage transfer have been established for the routine blind transfer technique of catheter introduction into the uterine cavity when a patient produces a large number of oocytes or has proven capacity to produce blastocysts. However, recent recommendations in using lower medication dosages for the controlled ovarian hyperstimulation, and in patients with lower response or advanced age, the number of developing embryos are limited and cleavage stage embryo transfers may be more advantageous. Also, since a significant number of embryos develop poorly beyond day three, early transfer is clinically prudent.32 consecutive patients with Infertility of various origins underwent Hysteroscopic Endometrial Embryo Delivery (HEED) on day two or three or day five after fertilization. Controlled ovarian hyperstimulation was done using standard protocols. Transvaginal oocyte retrieval was performed under local anesthesia with mild sedation. All women received some type of luteal support, be it progesterone or hCG. Oocytes were fertilized and cultured in early cleavage medium (Irvine Scientific) at 37 degrees C and 5% CO2 in air. Embryos were transferred at 48-120 hours post fertilization.The percent of total ongoing live births per transfer is not different between transfer on day two and three, and percent of ongoing pregnancies occurring with transfers on day five is higher than transfers on day three or two. (Chi square value for day two vs. five = 1.36, 0.5<p<0.1; chi square value for day three vs. five = 1.34, 0.5<p<0.1).Of pregnancies that occurred with transfer on day three, fifty percent resulted in miscarriage or biochemical pregnancy, while only sixteen percent had this result when transfer occurred on day two. Only one multiple pregnancy occurred with day of transfer two and five, while none of the transfers on day three produced a multiple pregnancy. Finally, no ectopic pregnancies were observed in either group.These results using Hysteroscopic Endometrial Embry Delivery (HEED) show for the first time that the technique is very effective with both cleavage stage embryos and blastocysts, including day two embryos. These results are even more remarkable due to our clinical bias to replace embryos on day 2 when presented with poor quality or low numbers of embryos. Our findings could offer new hope of success for a large number of poor prognosis IVF patients.