RESUMEN
<p><b>OBJECTIVE</b>To investigate the differences in the development of primordial germ cells (PGCs) between male and female mouse embryos.</p><p><b>METHODS</b>The morphological changes of genital ridge development were detected in C57BL/6J mouse embryos of 11-13.5 days, and the changes of PGCs quantity and proliferation were compared between the male and female embryos using immunofluorescence histochemistry.</p><p><b>RESULTS</b>The PGCs was the most numerous at 13.5 days in male and female embryos, and the quantity of proliferating PGCs reached the maximum at 13 days. The quantity of PGCs and proliferating PGCs in male embryos at 13 days was significantly larger than that in female embryos.</p><p><b>CONCLUSION</b>The development of PGCs is characterized by a gender differences in early development of mouse embryos (11-13.5 days).</p>