The ability to modulate cellular function by the transfer and expression of novel genes or by affecting the levels of endogenous proteins by genetic means has been of tremendous benefit in studying cellular functions and offers great promise in the treatment of a variety of diseases. Consequently, the development of novel and efficient nonviral DNA delivery systems is an important goal. Small cationic peptides, termed peptide/protein transduction domains (PTDs), effectively deliver a wide variety of cargoes, including DNA, into all cells. Expression of the human immunodeficiency virus type 1 (HIV-1) TAT PTD on the surface of bacteriophage λ results in the efficient delivery of plasmid DNA into a variety of cells in a concentration-dependent manner without cytotoxicity. This protocol describes the preparation of recombinant λ particles with a TAT peptide transduction domain sequence on their surface and the use of these particles in delivery of plasmid DNA into a variety of cells.