Gene therapy offers a new treatment paradigm for curing human disease. Rather than altering the disease phenotype by using agents that interact with gene products, or are themselves gene products, gene therapy can theoretically modify specific genes, resulting in disease cure following a single administration. Initially gene therapy was envisioned for the treatment of genetic disorders, but is currently being studied for use with a wide range of diseases, including cancer, peripheral vascular末梢血管のdisease, arthritis, neurodegenerative 神経変性の disorders and other acquired diseases. Certain key elements are required for a successful gene therapy strategy. The most elementary of these is that the relevant gene be identified and cloned. Upon completion of the Human Genome Project, gene availability will be unlimited. Once identified and cloned, the next consideration must be expression of the gene. Questions pertaining to the efficiency of gene transfer and gene expression remain at the forefront of gene therapy research, with current debates revolving around the transfer of desired genes to appropriate cells, and then to obtaining sufficient levels of expression for disease treatment. With luck, future research on gene transfer and tissue-specific gene expression will resolve these issues for the majority of gene therapy protocols. Other important considerations for a gene therapy strategy include a sufficient understanding of the pathogenesis of the targeted disorder, potential side effects of the gene therapy treatment, and a more in depth understanding of the target cells which are to receive gene therapy. Gene transfer vector is the mechanism by which the gene is transferred into a cell. Currently there are at least 150 clinical gene therapy protocols worldwide. Since the approval process for these protocols is not as public outside the U.S., it is difficult to ascertain the exact number of worldwide protocols. As of December 1995, 1024 patients had been treated with gene therapy protocols. Much controversy exists regarding how many of these patients have benefited from their gene therapy, and no one has yet been cured. Public controversy in the field of human gene therapy is driven by several factors. Ordinary citizens as well as scientists easily understand the enormous potential of gene therapy, but the former may not appreciate all the pitfalls and uncertainty that lie in the immediate future. The financial interests of biotechnology firms and, some have asserted, the career interests of some gene therapists have encouraged extravagant, or at least overly optimistic public statements about contemporary gene therapy. In spite of the proliferation of protocols, the actual number of patients treated remains small, and only one genuinely controlled study of human gene therapy has been published as of this date.