Abstract: Mouse parthenogenetic embryonic stem cells (pES) were isolated from mouse parthenogenetic blastocysts by the immunosurgical method and the differentiation potential of pES was investigated in vivo and in vitro. The results showed that: mouse pES isolated from mouse parthenogenetic blastocysts have the ability to proliferate at least 25 generations in vitro and show very strong activity of alkaline phosphate enzyme. The karyotype of pES was showed as 40XX. To investigate the diffenentiation potential of mouse pES in vivo, pES at the 18 generation were trypsinized and transferred into the testicle envelope of Kunming mouse, histomorphological analysis showed that pES maintained the developmental potential to differentiate into advanced derivatives of all three primary germ layers ectoderm, endoderm and mesoderm in vivo. Immuno histochemistrical results showed that mouse testis had Neuron specific enolase (NSE) and muscle specific ?-actin positive cells which derived from pES. Mouse pES at 20 to 24 passages were directionally induced to differentiate in vitro. The results showed that they can be induced into nerve cells and myocardial cells with the rhythm of contraction. Immunocytochemistry showed that myocardial cells were ?-actin positive and nerve cells were NSE positive. These data indicated that mouse pES can be directionally induced into ectoderm and mesoderm-derived cells in vitro. In conclusion, mouse pES cells were successfully isolated from parthenogenetic blastocysts by immunosurgical method and they have pluripotent in vivo and in vitro.