A method and apparatus for electroporation includes placing a mixture of bacterial suspension and transforming DNA into an electroporation cuvette. The resulting sample is subjected through a current-limiting device to a complex 5 waveform including a burst of high-voltage radio-frequency current, which in some embodiments is superimposed on a biphasic high-voltage DC pulse, and in other embodiments on a high-voltage lower-frequency AC burst. The total waveform has at least an initial portion greater than eleven thousand volts per centimeter of electrode spacing, and a later portion in some embodiments is reduced to less than thirty percent 10 of magnitude of the initial portion. Transformed bacteria are selected by culture in selective medium in an embodiment. The high-voltage radio-frequency current is between 3 and 125 MHz, and in an embodiment is 24 MHz.