The present investigation was to identify the signaling and metabolic pathways of expressed genes by microarray comparison between Primordial Germ Cells (PGCs) and their somatic counterpart, chicken embryonic fibroblasts (CEFs). We identified a total of 2,605 expressed transcripts. Among these, 1,197 were predominantly expressed in PGCs, and 1,408 were predominantly expressed in CEFs. Overall design: Cell culture and microarray data generation were performed in triplicate. Blood PGCs from E2.5 embryos (N=20 for each replication) and CEFs from E6.5 embryos (N=5 for each replication) were cultured in appropriate culture medium. Total RNA was extracted from cultured PGCs (1,500,000 cells for each replication) and cultured CEFs (6,000,000 cells for each replication) with a Qiagen RNeasy kit. About 5 µg of total RNA from each replication was used for labeling. Probe synthesis from total RNA samples, hybridization, detection, and scanning were performed according to standard protocols from Affymetrix.