The aim of gene therapy includes the tight spatial and temporal control of transgenic expression. There are several approaches concerning the externally inducible gene promoters used for the control of suicide genes. We have tested the mifepristone-dependent system GeneSwitch to regulate the expression of a deletion mutant of Pseudomonas exotoxin A in the hypopharyngeal carcinoma cell line, FADU. The GeneSwitch system consists of two plasmids, the regulatory plasmid, pSwitch, and the pGene/V5-His plasmid, in which we cloned the toxin mutant (pGene/V5-His-ETA). We stably transfected FADU cells with pSwitch and subsequently transiently separated pSwitch clones with pGene/V5-His-ETA. We tested the inductive capacities of single pSwitch clones, the influence of experimental variations in transfection, the inductive capacities without antibiotic selection pressure, the inductive capacity after re-induction, as well as the background expression levels. In FADU cells the GeneSwitch-ETA combination worked precisely and effectively. Our in vitro study revealed that the use of toxin genes in combination with the GeneSwitch system is a promising approach for gene therapy in head and neck cancer.