RNA interference appears as a promising tool for therapeutic gene silencing to block protein expression. A long-lived silencing is obtained through the in situ expression of shRNA. A safe approach is to use a physical method such as in vivo electropulsation with plate electrodes. This is presently validated in muscles by the in vivo coelectrotransfer of plasmids specifically coding for expression and silencing of a fluorescent protein. No long-lived tissue damage is observed by the proper choice of the electric pulsing parameters and the amount of injected plasmids. Using a noninvasive fluorescence imaging assay, electrodelivery in mouse muscles is observed to induce complete silencing over more than 2 months in a specific way. The proper choices of the plasmids (sequence, promoter, and relative amounts) appear as key parameters in the successful long-term silencing.