Gene Therapy is a technology by which genes or small DNA or RNA molecules are delivered to human cells, tissues or organs to correct a genetic defect, or to provide new therapeutic functions for the ultimate purpose of preventing or treating diseases.

Although the term gene therapy is often associated to the concept of genetic modification or manipulation of the human genome, the most common use of this technology implies addition of new genetic information to human cells rather than alteration of their genome.

The most comprehensive description of gene therapy is therefore the use of recombinant genetic material (DNA, RNA or hybrid molecules)under different forms or pharmaceutical preparations, as a therapeutic agent.