A new method for biolistic delivery of nucleic acids using a combination of cationic micro- and nanoparticles is reported. The new method is simpler to perform than the conventional calcium/spermidine-based formulations and shows 11-fold improved nucleic acid binding capacity and dose-dependent performance both for in vitro and in vivo applications relative to either the conventional preparation or our recently reported direct cationic microparticle method. These features may enable higher throughput gene delivery and genetic immunization programs and open new venues for the biolistic delivery method.