Since the Atomic Energy Act of 1946, the Office of Biological and Environmental Research (OBER) and its predecessors have supported a broad-based, multidisciplinary research program to define human health risks from energy technologies. Between 1946 and 1974, the research was related to health effects of radiation. With the creation of ERDA, then DOE, the program was expanded to include potential health risks from other energy technologies including combustion and conversion of fossil fuels and electromagnetic fields. One focus has been on epidemiological studies of human populations. Studies on human populations exposed to radiation have included atomic bomb survivors, naval shipyard workers, employees at weapon design and production sites, uranium miners, radium dial painters, and soldiers present during weapons tests in Nevada. Taken together, these epidemiological studies form the core of what we know today of radiation exposure risks. Other epidemiological studies have included workers exposed to coal conversion effluents and diesel exhaust. Animal studies have also been conducted to extend and refine available human data. This included studies to understand the fate and potential health effects of ingested or inhaled radionuclides produced in the nuclear fuel cycle. The animal studies have also expanded the knowledge base on the effects of exposure to different types of radiation and the effect of dose rate and influence of the age of exposure on the effects of exposure. During the 1970s and 1980s, extensive studies in cells and animals were conducted to define hazards and risks of effluents from fossil-fuel combustion and conversion. An outgrowth and extension of these epidemiological and animal studies have been detailed studies on biological mechanisms that result in health effects. This has included studies on genetic susceptibility, gene injury and repair, biochemical changes, immune responses, cellular and tissue responses, changes in organ function, and species differences. This OBER-sponsored research has been used to assess health risks for most energy technologies and the potential consequences of radiation accidents such as Three Mile Island and Chernobyl. It is also the basis for worker-protection standards, and environmental limits for air, soil, water, and emissions. Finally, it forms a basis for the detection and prevention of diseases. For example, the Human Genome Project is an offspring of this research on health effects. (The research summarized in this abstract has been conducted by scientists from most DOE laboratories and many universities.)