Since Louise Joy Brown, the first baby of In Vitro Fertilization-Embryo Transfer (IVF-ET), was born in the United Kingdom in 1978, there had been over five million successful cases over the course of 35 years. There are two commercially available culture media in the market: Single Step Medium (Global Medium) and Sequential Medium (Sage Medium). The development of these two media had enhanced the quality of embryo and increased the pregnancy rate in IVF-ET. In this collection of 210 cases of IVF-ET, oocytes were fertilized by intracytoplasmic sperm injectionï¼ICSIï¼and randomly assigned to the two commercially-available culture media. The quantity and quality of embryos were observed and recorded for three consecutive days in order to compare the development of embryos in the two commercial culture medium. A fertilized rate of 75.5% in Global Medium and 77.5% in Sage Medium were observed on the first day. There was a higher number of cleaved cells in Global Medium and embryos of Grade 1 cells than those in Sage Medium both on the 2nd and the 3rd day, though no significant differences were noted in the pregnancy rates between the two samples. In the group of those over 38 years old, there was a higher number of cells in Global Medium, but exhibited no difference in either embryonic pattern or in the pregnancy rate. Though the development of commercial culture medium had enabled a longer cultivation, some cases still failed be cultured to the blastocytic stage due to other limitations. It had been attempted with morphologic selection in embryos by the 3rd day of culture, with a criteria of over six cells per embryo and minimal cell fragmentation, to reach compatible pregnancy rate of embryo implantation of the 5th day by conventional method. Our study indicated that the there was higher number of Grade 1 embryos with more than 6 cells and lower embryo fragmentation in Single Step Medium, thus yielded a better overall quality of embryo than Sequential Medium. It can be speculated, therefore, that the Single Step Medium would offer a valuable choice in patients with difficulty in reaching blastocytic stage by conventional method due to various factors. Advisors/Committee Members: Lee Su-long (chair), Liu, Jong-Kang (committee member), Chang Chi-Chang (committee member), Chen, Chun-Lin (chair).