Abstract Available data suggest that gene regulation by the Gata-1 Hematopoietic Regulatory Domain ( Gata-1-HRD) is limited to cells derived from the erythroid lineage. This characteristic makes Gata-1-HRD a candidate for control of cre expression in conditional knock-in and knock-out models in which erythroid-specific gene expression is essential. To characterize the specificity of Gata-1 HRD regulation of cre, transgenic mice expressing improved cre recombinase (iCre) under the control of Gata-1-HRD were generated. The founders were crossbred with mice that have an inactive loxP-containing β-galactosidase gene that can be rescued by the cre recombinase. The β-galactosidase activity was detected in the marrow of this crossbred mouse, but no activity was observed in other organs. To identify the cre expressing cells in marrow, double-immunostaining of marrow sections with anti-β-galactosidase, and antibodies against various hematopoietic lineage markers or erythropoietin receptor (epor) was performed. The epor positive cells in marrow expressed β-galactosidase, but megakaryocytic precursors and nonerythroid epor-positive cells in brain and spleen did not. We conclude that when cre is under control of Gata-1-HRD, its expression/function is limited to erythroid progenitors. The knock-in and knock-out models utilizing Gata-1-HRD-iCre, can be explored for the studies of erythroid-specific gene expression.