Field characterization for HDR/HWR entails a number of studies in various academic fields prior to, or at the initial stage of HDR/HWR development. Although guidelines are not yet well defined, field characterization will be important for the efficient progress of HDR/HWR research on both a laboratory and field scale. The decision might be taken to stop a project based on new knowledge obtained during development in order to minimize the total risk of the project. This paper is an overview of field characterization in HDR/HDR research throughout the world since 1982. The HDR/HWR field experiments, temperature of the targets, regional and local geology, evaluation of fracture distribution in the exploration stage, and geochemistry for reservoir maintenance, will all be reviewed.