This study was designed to examine the factors affecting in fertilization and development of embryos in vitro, and to examine whether zone drilling by laser irradiation can improve the hatching rate of IVF embryos from DNA marker-proved Hanwoo. DNA markers related to marbling score were identified using DNA fingerprinting with Ml3 probe and restriction enzyme Hae III. Oocytes were aspirated from immature ovarian follicles using a combined method of rectal ovarian-palpation and transvaginal ultrasound-guidance(6.5MHz) under local anesthesia. The aspirated oocytes were washed twice with fresh D-PBS containing 5% FBS and were rewashed 4 to 5 times with TCM-199 containing 5% FBS. A morphological grade of I to IV was assigned to each oocyte. Data were analyzed using the GLM procedure of SAS. Sperm separation methods did not have any significant effect on cleavage or developmental abilities of IVF embryos. Significantly(P<0.05) higher cleavage rate was observed in embryos from GI(60.0%, 3/5), GII(69.2%, 18/26) and GIII(62.1%, 59/95) compared to embryos from GIV oocytes(36.2%, 25/69). And the developmental rate to blastocyst stage was higher(P<0.05) in embryos from GI(33.3%, 1/3) and GII oocytes(38.9%, 7/18) than those from GIII(16.9%,10/59) and GIV oocytes(4.0%, 1/25). There was no significant difference in development of IVF embryos to blastocyst by media for in vitro culture. Proportion of hatched blastocyst was significantly(P<0.05) higher in embryos received zona drilling by laser than those of non-drilled.