Holdren's knowledge and involvement in fusion goes back to the early 1970s, when he published a paper "Analytic Approximation to Collisional Distribution in Mirror Plasmas" while working as a theoretical physicist in the Magnetic Fusion Energy Division of the Lawrence Livermore National Laboratory. He joined the University of California, Berkeley, as an Assistant Professor of Energy and Resources in 1973. In the 1970s and early 1980s, he also wrote several papers on environmental and safety issues associated with future fusion power plants. In 1989, he chaired the "Senior Committee on Environmental, Safety, and Economic Aspects of Magnetic Fusion Energy." That report (UCRL-53766) stated that the "advantages (of fusion) are potentially large enough to make a difference in public acceptability of magnetic fusion energy, as compared to fission."

Holdren was a member of the President's Committee of Advisors on Science and Technology (PCAST) from 1994-2001 under President Clinton. In 1995, he chaired a PCAST Panel on the U.S. Fusion Energy R&D Program that stated, "Fusion R&D is an important investment in developing a needed new energy source, sustaining strong science, and building international cooperation." The panel stated, "Fusion would add an inexhaustible, site-independent source (of energy), without coal's pollution or biomass's land constraint, better safety/wastes/proliferation than fission, (and) probably cheaper than photovoltaics."

In 1997, Holdren chaired another PCAST study, "Federal Energy Research and Development for the Challenges of the Twenty-First Century." That report recommended a broad portfolio of energy programs, including Efficiency, Fission, Fossil, Fusion and Renewables. With respect to fusion, the panel recommended a $100 million increase in the fusion budget over the FY1997 level of $232 million.

Holdren was trained in engineering and plasma physics at MIT and Stanford. He co-founded and co-led an interdisciplinary program in energy and resources at the University of California, Berkeley, 1973-1996 and then took up his present post at Harvard University. He has published several books on energy and the environment and served as chair of the National Academies' Committee on International Security and Arms Control, 1993-2004.