First, to understand the ethical issues of gene therapy and anticipate the problems related to its future use, a survey was conducted among human genetics researchers in the USA. This survey provided systematic insight into the recurring moral concerns of the field. As a result, the findings reveal a strong approval of using somatic gene therapy to treat serious diseases in both adults and children. At the same time, there is still some debate over where to draw the line between therapeutic intervention and human enhancement. Although there is some support for germline gene therapy as a concept, those surveyed who were willing to take a risk most emphasized concerns about the unpredictable long-term consequences. Among other challenges is determining the proper criteria for disease prioritization, especially when weighing rare monogenic disorders against common multifactorial diseases. Therefore, this chapter primarily addresses the moral issues associated with somatic gene therapy.