Although in vivo electroporation is currently an unfamiliar nonviral means of gene transfer, accounting for only about 1% of total studies related to in vivo gene transfer and gene therapy, it may be extensively used for experimental and therapeutic purposes in the near future. Like other nonviral methods, in vivo electroporation has a variety of advantages over viral vectors as: any types of cells and tissues in theory could become a target, handling is easy and quickly done within a matter of second, repeated administration of DNA is possible, no immunogenicity is expected, and there is no constraints on amounts and sizes of DNA to be used. Gene transfer efficiency of in vivo electroporation was found to be equivalent to or even superior to that of in vivo lipofection, gene gun and direct DNA injection methods. Although gene expression exerted is transient and foreign genes are likely to be present in an episomal form when transferred by in vivo electroporation, foreign gene products could be detected for more than 1 month depending on tissues and DNA constructs used. Gene expression generated by in vivo electroporation could be controlled to a certain extent in a tissue-or cell-specific manner, and be induced as intended. Perhaps better appraisal of in vivo electroporation as a nonviral gene transfer method should be brought forth in the future after more detailed analyses.