The development of nonviral methods for efficient gene transfer to the lung is highly desired for the treatment of several pulmonary diseases. We have developed a noninvasive procedure using electroporation to transfer genes to the lungs of rats. Purified plasmid (100-600 microg) was delivered to the lungs of anesthetized rats through an endotracheal tube, and a series of square-wave pulses were delivered via electrodes placed on the chest. Relatively uniform gene expression was observed in multiple cell types and layers throughout the lung, including airway and alveolar epithelial cells, airway smooth muscle cells, and vascular endothelial cells, and this finding was dose- and pulse length-dependent. Most important, no inflammatory response was detected. To demonstrate efficacy of this approach, the beta1 subunit of the Na(+),K(+)-ATPase was transferred to the lungs of rats with or without electroporation, and 3 days later, alveolar fluid clearance was measured. Animals electroporated with the beta1 subunit plasmid showed a twofold increase in alveolar fluid clearance and Na(+),K(+)-ATPase activity as compared with animals receiving all other plasmids, with or without electroporation. These results demonstrate that electroporation is an effective method to increase clearance by introducing therapeutic genes (Na(+),K(+)-ATPase) into the rat lung.