This experiment was investigated the effect of presence of granulosa cells from follicles of different size on bovine oocyte maturation, cleavage and development to late stage. The nuclear and cytoplasmic maturation of oocytes in the IVM-IVF system are critical for subsequent embryo development. Granulosa cells when the co-cultured with oocytes may interact with cumulus-oocytes complexes and influence the development competence of the oocytes. Granulosa cells from medium (2~6 mm) and large(>1O mm) size follicles were recovered by aspiration, washed 3 times by centrifugation at 500 x g for 5 min. and used for co-culture at a concentration of 2~3 x 106 cells/mi. The oocytes were matured in vitro (IVM) for 24 hrs. in TCM-199 supplemented with 35 $mu$g/ml FSH, 10 $mu$g/ml LH, 1 $mu$g/ml estradiol-17$eta$ and granulosa cells at 39$^{circ}C$ under 5% $CO_2$ in air. They were fertilized in vitro (IVF) by epididymal spermatozoa treated with heparin for 24 hrs., and then the zygotes were co-cultured in vitro (I VC) with bovine oviductal epithelial cells for 7 to 9 days. The assessment of maturation revealed that Grade J oocytes showed significantly(P<O.05) more expanded cumulus cell(93.O% of 158 oocytes) than Grade II oocytes(79.4% of 107 oocytes). Following in vitro fertilization, the proportion of zygotes cleaved was higher (P <0.05) in Grade I oocytes(84.1%) than in Grade II oocytes(61.5%). The co-culture of Grade I oncytes with granulosa cells for IVM improved significanly (P<O.05) the subsequent development to morulae and blastocysts(33.6%), compared with the control oocytes (19.2%). The effect of co-culture with granulosa cells was similar to the oocytes from the medium(31.6%) or large(33.6%) follicles. It was concluded that the presence of cumulus cells surrounding immature oocytes and the addition of granulosa cells to culture medium might be required to induce both nuclear and cytoplasm maturation of bovine oocytes more effectively.