Chitosan-DNA nanoparticles were synthesized from the complexation of chitosan solution and the plasmid pCD-GFP encoding green fluorescent protein through a coacervation process. The nanoparticles formed were of diameter inferior to 100 nm. The transfection efficacy of chitosan-DNA nanoparticles in MGC803 cells was higher than in SMMC-7721 cells, whereas the plasmid GFP was not expressed in MG63 cells.