Protoplasts provide a convenient system for introduction of nucleic acids into plant cells. Protoplasts allow rapid assays of gene expression and virus replication, with advantages for plant biology similar to those of cultured animal cells for the study of animal systems. Traditionally, preparation and handling of protoplasts has been as much art as science, requiring a special touch by the user. The purpose of this unit is to lay out in clear detail all the methods and nuances involved in protoplast preparation using a robust, reliable system that does not require skills beyond those expected of an unspecialized molecular biologist. Because dicots and monocots differ in many biological properties, and because different procedures may work better for different plants, separate units in this chapter are devoted to protoplast preparation from dicots (Arabidopsis, tobacco; refer to UNITS 16D.1 & 16D.4) and from a monocot (oat). This unit describes methods for preparation and transfection by electroporation of protoplasts derived from an oat suspension culture.