A temperate, type IV pilus-dependent, double-stranded DNA bacteriophage named DMS3 was isolated from a clinical strain of Pseudomonas aeruginosa. A clear-plaque variant of this bacteriophage was isolated. DMS3 is capable of mediating generalized transduction within and between P. aeruginosa strains PA14 and PAO1, thus providing a useful tool for the genetic analysis of P. aeruginosa.