Bovine oocytes obtained from follicles(2~5mm) of ovaries after slaughter were cultured in TCM 199 medium with 10~20% heat-inactivated estrus cow serum(ECS) for 25~27 hr, at 39$^{circ}C$ under 5% CO2 in air. At the end of culture period, some oocytes were stained with 1% acetoorcein and examined for the evidence of oocyte maturation. The remainder were used to assess the potential of in vitro fertilization(IVF) with frozen-thawed spermatozoa and subsequent development in media with or without bovine oviduct epithelial cell (BOEC) co-culture. The results obtained were summarized as follows ; 1. The maturation rate of oocyte in vitro in TCM 199 medium with 15% ECS group(76.3) was superior to 10% ECS group(68.3%) and 20% ECS group(64.5%). 2. The IVF rates of oocytes matured in vitro, and formation rate of male and female pronuclei were 63.6%(77/121) and 93.5%(72/77), respectively. The incidence of polyspermy was very low(2.4%). 3. Of 73 oocytes fertilized in vitro and cultured in TCM 199 medium with 10% fetal calf serum for 7 days, 41(56.3%) were cleaved over 2-cell and only 1(2.4%) was developed beyond the 16-cell stage. 4. Of 76 oocytes co-cultured with BOEC, 58(76.3%) were cleavaged and 23(39.7%) were developed to morula and blastocyst stage. The results of this study indicate that co-culture with BOEC deserved a positive effect on the IVF oocyte development through the 16-cell block.