Introduction of foreign genes into plant cells can be achieved by a variety of methods, including direct transfer into protoplasts using chemical (1–3; see also Chapter 7, this volume) and electrical methods (4–6). These methods can be used to study genes both transiently (1, 5,7) and when stably integrated in regenerated transgenic plants (2– 4, 6). The electrical method (electroporation) is a simple and rapid procedure and involves applying electrical pulses to a suspension of protoplasts and DNA placed between electrodes in a suitable cuvet. The electrical pulses induce the formation of transient pores in the plasmalemma allowing DNA to enter the cell and nucleus. The method has been used to introduce genes into protoplasts isolated from a range of different species and seems to be a universal method of gene transfer into prokaryotic and eukaryotic cells (an application of the technique to transform Agrobacteria is covered in Chapter 2, this volume).