In 1997, after long social debates, the Japanese government enacted a law on organ transplantation from brain-dead bodies. Since 1993, on gene therapy, administrative agencies have issued a series of guidelines. This study seeks to elucidate when people became aware of the issues and when they formed their opinions on organ transplant and gene therapy. At the same time, it aims to examine at which point in time experts, those in university ethical committees and in academic societies, consider these technologies (...) became accepted among the public. A self-administered questionnaire was sent by mail to a stratified random sampling of 3000 people nationwide in Japan. Another questionnaire was sent both to the member societies of the Japanese Association of Medical Sciences and to the ethical committees of all the medical schools in Japan. Results of the surveys indicated that many of the public remained undecided on the desirability of organ transplant or gene therapy at the time of enactment of official guidelines. A substantial part of them formed their opinions in subsequent periods, especially around the time of first implementation and thereafter. Experts of the academic societies and of the university ethical committees regarded the time of implementation as an important factor in the acceptance of the technologies in society. Since many people formed their opinion during the period of technological implementation, communications efforts to facilitate public understanding of science and technology, as well as to advance practical discussion on policy alternatives in this period can play a key role in determining the fate of technological innovation and ethical debates in medicine. (shrink)