This study was carried out to improve pregnancy rate in IVF-ET program through Assisted Hatching (AH) by the use of micromanipulation technique. Among 72 IVF patient, randomized 29 IVF patients were performed for AH by Partial Zona Dissection(PZD). Two to eight cell embryos were micromanipulated just before uterine transfer. The results were as follows: 1. The implantation rates of embryos between PZD group and control group were 10.0%, 4.9%, respectively. 2. The clincal pregnancy rates of both groups were 34.5%,20.9%, respectively. 3. Among 131 PZD embrys, only 2 embryos were damaged mechanically. Although there were no statistical difference in the rates of implantation and pregnancy between PZD group and control group due to small sample size, the PZD group had increasing trend in the rates of implantation and pregnancy. In conclusion, it would be thought that PZD could be adequately used to improve implantation rate and pregnancy rate in IVF-ET program as an assisted technique if much more studies were done. Also the risks resulting from this study can be reduced because of technical stability, which showed the low rate of damaged embryos.