Gene Pulser electroporation buffer is formulated to improve delivery of molecules into mammalian cells, especially primary cells and difficult-to-transfect cells. The sugar-based formulation simulates the natural cell environment to minimize cell mortality while ensuring efficient delivery of nucleic acids. It works with most waveforms and electroporation systems, and can be used for delivery of siRNA and plasmid DNA, in single cuvettes or in multiwell plates.