Nine embryonic stem cell lines have been established from mouse strain 129/ter. Three of the nine ES cell lines were karyotypically normal. The nine cell lines showed some difference in the growth rate and the differential competence. Chimeras were made by injecting the ES cells into C57BL/6J blastocysts, and the germline compositions of the chimeras were detected by mating them with albino ICR mice. The results indicated that ES cell line MESPU21 and MESPU22 were both highly germline-competent. Comparing with other ones, these two cell lines both were karyotypically normal and propagated fast. The tissue composition of the teratocarcinomas derived from these cell lines appeared paralle to the results of chimera production. Careful manipulation during the process of ES cell establishment was helpful to obtain good cell lines.