Primordial germ cells (PGCs) are precursors of germline cells. Although avian PGCs have been used to produce transgenic birds, their characteristics largely remain unknown. In this study, we isolated PGCs from chicken embryos at various developmental stages and analyzed the gene expression. Using the expression of stage-specific embryonic antigen-1 (SSEA-1) as a marker of chicken PGCs, we purified PGCs from embryos by fluorescence-activated cell sorting after incubation for 2.5-8.5 days. The number of SSEA-1(+) cells was almost unchanged during days 2.5-8.5 of incubation in females but continuously increased in male. Expression of several genes, including Blimp1, SOX2, and CXCR4, was observed in SSEA-1(+) cells but not in SSEA-1(-) cells in both female and male embryos. Quantitative reverse-transcription PCR analysis revealed that the expression of CXCR4, a chemokine receptor essential for migration of PGCs from the bloodstream to the gonads, was reduced after the circulating PGC stage (day 2.5).