These mxperiments were carried out to investigate the effect of rabbit anti-bovine cumulus cell antibodies on in vitro fertilization and following development of bovine follicular oocytes matured in vitro. The bovine ovaries were obtained at a slaughter house and the follicular oocytes surrounded by cumulus cells were collected by puncturing follicles with 2~6mm of diameter. Bovine oocytes were matured in vitro for 24~26hrs in a CO2 incubator with 5% CO2 in air at 39$^{circ}C$ and subsequently cultured in medium containing cumulus cell antibody for 1 hour. The medium used for maturation was TCM-199 supplemented with hormones, pyruvate, FCS and antibiotics. Epididymal spermatozoa were capacitated by in vitro culture for 2~3 hrs in BO solution 10~15 matured oocytes into the suspension of capacitated spermatozoa. Six hour after insemination the eggs were transferred to TCM-199 supplemented with FCS(10%) and then cultured for 7 days. The results obtained in these experiments were summarized as follows : 1. When the follicular oocytes matured in vitro were treated with antibody to intact cumulus cells, the fertilization rate of cumulus intact and removed oocytes was ranged to 45.0 to 53.7%. These value is slightly lower than that(64.3%) of follicular oocytes not treated with the antibody, and increased frequency of both male and female pronuclear formation was found in cumulus intact oocytes cultred in medium without the antibody(p<0.05). 2. The fertilization rate of cumulus intact and removed oocytes treated with antibody to solubilized cumulus cells was ranged 45.0 to 52.5%, significantly lowre than that(62.8%) of oocytes cultured in antibody free medium, and increased frequency of ova with male and female pronuclei was found when cumulus cells were present(p<0.05). 3. The rates of cumulus cell intact and removed oocytes developed to 8-, 16-cell and morula or blastocyst after treatment of intact and solubilized cumulus cell antibody were ranged 7.1 to 14.5, 2.9 to 5.9 and 1.5 to 2.9%, respectively, slightly lower than 18.6, 10.0 and 8.6% of cumulus intact oocytes cultured in medium without the antibody. The results of this stduy indicate that cumulus cells promote not only normal fertilization with proper pronuclear formation, but embryo development and that the beneficial effect of cumulus cell to the pronuclear formation and embryo development is blocked by the action of antibody to cumulus cell.