['Long-term expression of the delivered target gene is critical for successful gene therapy. Recently, hepatic control region I (HCR I) originating from the apolipoprotein (apo)C-I pseudogene was shown to be a critical element for long-term gene expression in the liver of mice. HCR II is another hepatic control region of apoC-I.', 'HCR I, HCR II and HCR I/II-containing plasmids encoding factor IX were prepared and hydrodynamically transferred into the liver of normal and hemophilia B mice. Factor IX expression, clotting activity and formation of antibodies against the expressed gene product were compared.', 'HCR I-, HCR II- and HCR I/II-containing plasmids all induced long-term gene expression in both normal and hemophilia B mice. Post-transfection factor IX expression in the hemophilia B mice remained above 500\u2009ng/ml for 210\u2009days. Antibodies against human factor IX were detected at a low level in the serum, although they had no effect on the levels and clotting activity of the expressed factor IX.'] Do hepatic control elements promote long-term expression of human coagulation factor IX gene in hydrodynamically transfected mice?