The use of promoters that strongly express target genes in the chicken oviduct is beneficial for the production of proteinaceous materials into egg white by transgenic chickens. To examine the regulatory mechanisms of chicken lysozyme gene expression in vivo, genetically manipulated chickens that express human erythropoietin under the control of a lysozyme promoter-enhancer were established. By using several deletion mutants of the promoter-flanking region, we found that a -1.9 kb DNase I hypersensitive site (DHS) was essential for oviduct-specific expression in genetically manipulated chickens. The concentration of human erythropoietin in egg white was 14-75 μg/ml, suggesting that the chicken lysozyme promoter containing -1.9 kb DHS is sufficient for the production of pharmaceuticals using transgenic chickens.