In this section we describe some of the diseases where gene therapy approaches are being developed in an effort to find effective treatments. The diseases have been categorized into three classes: cancer, genetic disorders and infectious disease. The purpose of this section is to briefly introduce the target diseases to non-specialists and the approaches that have been adopted in the gene therapy field to treat them. This section serves as an educational resource for those who wish to learn more about the rationale behind the development of genetic therapeutics.