Objective To study the factor affecting the efficiency of establishment of parthenogenetic stem cells(PESCs) in mice.Methods PESC lines were derived from parthenogenetically activated blastocyst inner cell mass of different mice strains and cultured in different systems.Results The efficiency of establishing the pESC showed no significant difference in hybrid and inbred lines.But the efficiency was increased in culture systems added with ERK inhibitor or knockout serum replacement(KSR).Conclusion The effici...