When studying the contributions of Epstein-Barr virus (EBV) to tumorogenesis, it is often advantageous to analyze the effects of the expression of one viral protein on the host cell separately from the effects of other viral proteins that are being concurrently expressed during a normal infection. Electroporation is a method of introducing a plasmid expressing the viral protein of interest into cells and, for long-term studies, generating cell lines that stably express that viral protein. This chapter will present strategies for: 1) optimizing electroporation conditions for a given cell line, 2) determining the efficiency of transfection of that cell line under those optimized conditions, and 3) selecting for cell lines that stably maintain the introduced DNA. A method for determining the susceptibility of cell lines to drug selection—a prerequisite for generating cell lines stably maintaining a desired DNA and expressing a desired protein—will also be described.