The promise of effective gene therapy can only be accomplished by high-level expression and regulatable delivery of gene products. To achieve this end, a eukaryotic expression plasmid was modified to make transcription dependent on a tetracycline (Tc)-regulated chimeric transactivator. Mouse muscle injected with this two plasmid cis/trans control system expressed reporter proteins at levels five-to 10-fold greater than the cytomegalovirus immediate-early promoter-controlled parental plasmid. Tetracycline could be useful to either repress or activate transactivator-controlled expression based on the position of the tetO control sequences within the reporter plasmid. Finally, a prototype single plasmid construct was made and shown to express a self-regulating bicistronic transcript containing both the reporter and the transactivator. These Tc-controlled plasmids, termed maximum expression and regulated vectors (MERVs), have the potential to target a variety of gene therapy applications.