Methods and compositions are provided for modulating, e.g., reducing, expression of a target sequence in mammals and mammalian cells. In the subject methods, an effective amount of an RNAi agent, e.g., an interfering ribonucleic acid (such as an siRNA or shRNA) or a transcription template thereof, e.g., a DNA encoding an shRNA, is introduced into a target cell, e.g., by being administered to a mammal that includes the target cell, e.g., via a hydrodynamic administration protocol. Also provided are RNAi agent pharmaceutical preparations for use in the subject methods. The subject methods and compositions find use in a variety of different applications, including academic and therapeutic applications.
