Solomon A. Berson, M.D., the first Murray M. Rosenberg Professor and Chair of the Department of Medicine at Mount Sinai from 1968 until his death in 1972, and Rosalyn S. Yalow, Ph.D., 1977 Nobel Laureate in Medicine or Physiology and Solomon A. Berson Distinguished Professor-at-Large, brought meticulous quantitation and new vistas to all of clinical medicine and biomedical science through the application of their technique of radioimmunoassay. I was fortunate to know and work with them for many years. In 1972, while I was an NIH Fellow in gastroenterology at Mount Sinai, Dr. Berson suggested that I pursue my research in their laboratory at the Bronx Veterans Administration Hospital. Dr. Berson died one month after I began my research in the Bronx. Yalow and Berson had already discovered big gastrin (G-34), but much work with gastrin remained to be done. Challenging work with secretin, cholecystokinin, and a host of other gut peptides, would keep the Mount Sinai group at the forefront of this exciting field.