Nanoparticles consisting of DNA, human serum albumin (HSA) and polyethylenimine (PEI) were formed and tested for transfection efficiency in vitro with the aim of generating a nonviral gene delivery vehicle. HSA-PEI-DNA nanoparticles containing the pGL3 vector coding for luciferase as reporter gene were formed by charge neutralization. The particles were characterized by gel retardation assay, dynamic light scattering (size) and electrophoretic mobility measurements (charge). Stability was determined by spectrophotometric analysis and transfection efficiency was evaluated in cell culture using human embryonic epithelial kidney 293 cells. HSA-PEI-DNA nanoparticles were prepared by co-encapsulation of PEI as a lysosomotropic agent at varying nitrogen to phosphate (N/P) ratios. An optimum transfection efficiency was achieved when the particles were prepared at N/P ratios between 4.8 and 8.4. Furthermore, they displayed a low cytotoxicity when tested in cell culture. Our results show that HSA-PEI-DNA nanoparticles are a versatile carrier for DNA that may be suitable for i.v. administration.