The expression of POU-domain gene was detected in the central nervous system and the stages of nerve-related-organogenesis during early embryogenesis. The POU-domain gene products, or transcription factors, may exert critical function in the differentiation of special cell types as well as in the activation of specific programs of gene expression that determind specific cell phenotypes within a certain organ. The POU-domain gene expression during chick embryogenesis was analysed by hybridizing 32P-dCTP labelled chicken POU domain which was homologue of the conserved mouse POU-homeo gene, Brn with the total RNAs of 2 days, 7 days and 9 days chick whole embryos. Also the mRNAs of brain, liver, kidney and breast muscle of 12 days and 14 days chick embryos were analysed by using northern hybridization. Based on the results of dot and northern hybridization of chick embryonic RNAs and POU domain probe, it appears that POU-domain gene expression began from 2 days chick embryos and is gradually increased on to 9 days. Also the chick POU-domain gene is expressed in brain, kidney and breast muscle of 12 days and 14 days embryo. The expression of chick POU-homeo gene in kidney is much increased in 14 days embryo than in 12 days, but not detected in 12 days nor 14 days chick embryo in liver. As a conclusion, the expression of chick POU-domain gene appears to begin in early embryogenesis and to be reinforced later in the ectoderm related embryonic organs.