This oral history with Keith Yamamoto is one in a series documenting science and technology in Northern California. Its focus is Yamamoto’s years in the UCSF Department of Biochemistry which he joined in 1973 as a postdoc, rising to full professor in 1983. He recounts in detail his research on the glucocorticoid receptor and, more generally, on DNA transcription regulation. He was a first-hand witness to the invention and early application of recombinant DNA technology and the research breakthrough it represented as well as the public controversy it raised in the 1970s over its safety and commercialization. Yamamoto remains a persistent voice in issues pertaining to research ethics and responsibility in science. A second oral history recorded in 2014 chronicles his later career as UCSF Vice Chancellor for Research, Keith R. Yamamoto: UCSF Biochemist, Vice Chancellor for Research, and the Mission Bay Campus. A third oral history was recorded as part of the Sandler Foundation Project, Keith R. Yamamoto: The Sandler Foundation and the Program in Breakthrough Biomedical Research at UCSF.