Electroporation has been frequently adopted as a means to transfect primary cells or cell lines that demonstrate resistance to other commonly used methods of transfection, e.g., DEAE-dextran or calcium phosphate precipitation or liposome-mediated transfection. Electroporation is a method of transfection utilizing an electric field to introduce foreign materials into cells. This method of transfection has been demonstrated to be effective on both prokaryotic (1 –4 ) and eukaryotic cells (5 –8 ) and is capable of introducing DNA, large macromolecules (e.g., antibodies), proteins, dyes, metabolic precursors (e.g., 32 P-ATP), and nonpermeant drugs and metabolites into cells with high efficiency (4 ,8 –13 ).