Efficiency and reproducibility of gene electrotransfer depend on the electrical specifications provided by the pulse generator, such as pulse duration, pulse number, pulse frequency, pulse combination, and current intensity. Here, we describe the performances of GET42, a pulse generator specifically designed for gene electrotransfer into skeletal muscle. Expression of P-galactosidase in the Tibialis anterior muscle of Sprague-Dawley mate rats was increased 250-fold by GET42 compared to DNA injection alone. Combination of high and low current intensity pulses further increased transfection efficiency (400-fold compared to DNA injection without electrotransfer). Varying degrees of muscle necrosis were observed after gene electrotransfer. Nevertheless, muscle necrosis was dramatically reduced after optimization of cumulated pulse duration without significant reduction in transfection efficiency. Physiological applicability was illustrated by the analysis of cytochrome c promoter transactivation. In conclusion, GET42 has proven to be a reliable and efficient pulse generator for gene electrotransfer experiments, and provides a powerful mean to study in vivo the regulation of gene expression. (C) 2002 Elsevier Science (USA). All rights reserved.