Cationic polyethylenimine (PEI) derived transfection reagent is optimized for the delivery of genes to primary human hepatocytes and hepatocyte-like cells. Compatible with serum and antibiotics, jetPEI-Hepatocyte DNA transfection reagent has demonstrated transfection efficiencies of greater than 50% in primary hepatocytes. Similar transfection efficiencies have been shown in hepatocyte-derived cell lines such as BNL-CL.2 and HepG2. Galactose-bearing linear PEI enhances the transfection of cells expressing galactose-specific membrane lectins. Cell targeting is the result of binding of the galactose residues to the specific cell-surface receptors, leading to internalization of the DNA complexes. The protocol requires no media changes or washes. Transgenic protein expression is determined 24-72 hours post-transfection.