The objective of gene therapy for the treatment of cancer is to kill tumor cells but preserve normal tissue. A variety of strategies to achieve these aims have demonstrated promising results in the laboratory, including molecules that can specifically target pre-determined sequences in the DNA or RNAm; that sequences provide a means to modulate endogenous gene function. The different types of molecules: triplex forming molecules, antisense oligodeoxynucleotides, ribozymes, RNA interference, aptamers and decoys, are reviewed in this paper.