Poly(amidoamine)s with pendant primary amine (polymer 1a-1c) were evaluated as in vitro non-viralgene delivery vectors for bone marrow stromal cells (BMSCs). The cytotoxicity of these poly(amidoamine)s, measured by MTT assay, increased with increasing length of side chain, however, they were lesstoxic than branched polyethylenimine (PEI) 25 kDa. Using pGL-3 and pEGFP-C1 as luciferase gene andgreen fluorescent protein (GFP) gene, among all polycations including polymer 1a-1c and PEI, polymer1b at optimal N/P ratio showed highest luciferase expression (1.92×108 RLU/mg protein) as well aspercentage of cells expressing GFP (29.01±2.33%). For all polycations, intracellular trafficking of Cy3-labelled plasmid DNA (pDNA) was similar. Fluorescent particles attached to cell membrane at 0.5h afteradding the polycation/DNA complexes, aggregated in cytoplasm after 2h, and then stayed around theperinuclear region after 4h. pDNA nuclear localization appeared at 4h post-transfection, but much morepDNA entered into nucleus at 24h. At high N/P ratio, polymer 1a-1c could deliver pDNA into 70-80% ofBMSCs after 24h transfection, however, labelled pDNA was observed in only 4-25% of cells at the sametime. Compared to PEI, polymer 1b showed comparable or even higher percentage of pDNA uptake andnuclear localization. We concluded that poly(amidoamine)s with pendant primary amine, especiallypolymer 1b, are new kind of promising candidates of less toxic and highly efficient non-viral genedelivery vectors for BMSCs.