Current concepts and future developments in gene therapy are discussed from both scientific and social viewpoints. It is argued that from both the medical and the legal angle, gene therapy is analogous to organ transplantation. However, both the concept of disease and the therapeutic object must be determined with greater clarity. The history of gene therapy is outlined using pertinent examples. Lines of argument used by both supporters and critics of the development of gene therapy are examined and the divergence of views at the international level considered.