Public engagement in science and technology has grown in importance as developments in science and technology make increasingly significant impacts on people's lives. Now, efforts to engage publics in social decision-making or consensus-building regarding science and technology involve participation, learning or deliberation opportunities, as well as interactive or coproductive efforts among various sectors in society based on the recognition of scientific activities as a part of social operations - even those performed by scientific communities. We have conducted a community engagement (...) program in the HapMap project, the international human genome program, in Japan since 2002. Consequent upon our various approaches to engage Japanese publics, a range of observations were made, such as that: public engagement is not yet recognized or institutionalized in Japan; there is a wide gap between science and society; and the implications of public engagement in a Japanese context have not been examined enthusiastically, especially from the perspectives of political decision making, social consensus-building or self-determination. In this paper, we provide an overview of public engagement in Japan, and discuss issues and challenges raised by the HapMap community engagement project. We also discuss the implications of public engagement for social decision-making and self-determination, and explore the prospects for public engagement in science and technology in Japan. (shrink)