Objective: This study was to compare the characteristics between parthenogenetic mES (P-mES) cells and in vitro fertilization mES cells. Materials and Methods: Mouse oocytes were recovered from superovulated 4 wks hybrid F1 (C57BL/6xCBA/N) female mice. For parthenogenetic activation, oocytes were treated with 7% ethanol for 5 min and $5{mu}g$/ml cytochalasin-B for 4 h. For IVF, oocytes were inseminated with epididymal sperm of hybrid F1 male mice ($1{times}10^6/ml$). IVF and parthenogenetic embryos were cultured in M16 medium for 4 days. Cell number count of blastocysts in those two groups was taken by differential labelling using propidium iodide (red) and bisbenzimide (blue). To establish ES cells, b1astocysts in IVF and parthenogenetic groups were treated by immunosurgery and recovered inner cell mass (ICM) cells were cultured in LIF added ES culture medium. To identify ES cells, the surface markers alkaline phosphatase, SSEA-1, 3,4 and Oct4 staining were examined in rep1ated ICM colonies. Chromosome numbers in P-mES and mES were checked. Also, in vitro differentiation potential of P-mES and mES was examined. Results: Although the cleavage rate (${geq}$2-cell) was not different between IVF (76.3%) and parthenogenetic group (67.0%), in vitro development rate was significantly low in parthenogenetic group (24.0%) than IVF group (68.4%) (p<0.05). Cell number count of ICM and total cell in parthenogenetic b1astocysts ($9.6{pm}3.1,;35.1{pm}5.2$) were signficantly lower than those of IVF blastocysts ($19.5{pm}4.7,;63.2{pm}13.0$) (p<0.05). Through the serial treatment procedure such as immunosurgery, plating of ICM and colony formation, two ICM colonies in IVF group (mES, 10.0%) and three ICM colonies (P-mES, 42.9%) in parthenogenetic group were able to culture for extended duration (25 and 20 passages, respectively). Using surface markers, alkaline phosphatase, SSEA-l and Oct4 in P-mES and mES colony were positively stained. The number of chromosome was normal in ES colony from two groups. Also, in vitro neural and cardiac cell differentiation derived from mES or P-mES cells was confirmed. Conclusion: This study suggested that P-mES cells can be successfully established and that those cell lines have similar characteristics to mES cells.