Compositions and methods for targeted gene therapy are disclosed. Compositions containing double duplex-forming pseudocomplementary oligonucleotides are administered in combination with a donor oligonucleotide that is homologous to a target sequence on a double-stranded DNA molecule in need of repair or replacement. By activating cellular mechanisms involved in DNA synthesis, repair and recombination, the double duplex-forming pseudocomplementary oligonucleotides can introduce one or more mutations at a site of interest by increasing the efficiency of targeted recombination of the donor oligonucleotide. The pseudocomplementary oligonucleotides/donor oligonucleotide compositions may be administered in combination with a second therapeutic agent that enhances access of the pseudocomplementary oligonucleotides and/or the donor oligonucleotide to the target site, an agent that enhances or increases DNA repair or recombination, or an agent that enhances uptake or delivery of the oligonucleotides.