Robert S. Stone

Robert Spencer Stone (1895-1966) was a radiologist and headed the Health Division of the Chicago Metallurgical Laboratory (Met Lab) during the Manhattan Project.



Stone was born in Chatham, Ontario. He served in the Royal Canadian Air Force, and was wounded in action while fighting in Europe during World War I. He studied at the University of Toronto for both his undergraduate and graduate degrees, finishing with an MD in 1928. While studying medicine, he taught at the Peking Medical School in Beijing, and did his internship and residency at Grace Hospital in Detroit. He married in 1924. After receiving his MD, he joined the faculty of the University of California, San Francisco (UCSF). He was the first full-time radiologist at UCSF, and eventually became chairman of the department in 1939.

While at UCSF, he worked with several people who would go on to participate in the Manhattan Project, including Ernest Lawrence, Louis Hempelmann, and Hymer Friedell. He worked especially closely with Joseph Hamilton, with whom he conducted the first cancer therapy test involving artificial radioisotopes. Many of these partnerships were facilitated by the relationship and proximity between the University of California’s flagship campus at Berkeley and its only (at that time) medical school, UCSF. In addition to the work with Hamilton, Stone also pioneered neutron therapy (aided by the use of Lawrence’s cyclotron) and million-volt x-ray treatments for cancer, with mixed results.



Stone was personally hired by Met Lab Project Director Arthur Compton in 1942 to head the Health Division. He was one of the first physicians hired by the nascent Manhattan Project and held the title of Assistant Project Director. He initially divided his time between Chicago and San Francisco, but eventually joined full-time. He stocked the Health Division with his hand-picked associates and hired his old collaborator Hamilton (who continued to work at Berkeley). The Health Division eventually employed over 200 people.

The initial goals of the Health Division focused on occupational health and safety: developing monitoring instruments, shielding for what would become Chicago Pile-1, and treatment programs for pile-related health hazards. It evolved to include three groups: biological research, clinical medicine, and occupational health/health physics. This same structure was eventually adapted for the broader Manhattan Project.

Much of the research that Stone and his group did was in completely new scientific territory. They were tasked with setting standards for radiation and toxicity tolerance, based on very slim pre-war data. They had to investigate the hazards from fission products, about which almost nothing was known. The curative prescriptions for exposure to radioactive materials were, at the outset, “vacations, transfusions, and hope.” Exploring these new fields required new methods. Stone and his team invented a new unit for measuring radiation and its biological effect, called the “rem”; they conducted experiments on cancer patients that involved total body irradiation, a new procedure. He also exposed athritis patients to whole-body X-rays, an experimental procedure that was later condemned by the Atomic Energy Commission. His research goal was to understand the unknown effects of radiation on the body. 

One of the biggest unknowns was the new element being investigated at the Chicago site, plutonium. Plutonium was initially thought to be much safer than radium, but simply hard to detect. By 1945, however, Stone had concluded through animal studies that the toxicity of plutonium was 20 times higher than previously thought, especially because of its retention in key areas, such as bones. They also determined that absorption of plutonium through cuts was most dangerous, followed by inhalation, but that ingestion was not so bad. Stone held an significant role in overseeing the controversial human plutonium injections between 1945-1947. 

Stone had responsibilities at other Manhattan Project sites as well. The Met Lab ran a facility in Oak Ridge, and Stone appointed Simeon Cantril to be the Health Group’s representative there. Stone was also tasked with ensuring that other sites were staffed with radiation experts. The Health Group moved its operations to Oak Ridge in 1944, partly to assist with training these recruits. Stone did not always get along with medical leaders at other sites, and strove to maintain the Health Division’s independence. He clashed especially with the Manhattan Engineering District’s Colonel Stafford Warren over whether the focus of their efforts should be on near-term wartime needs or long-term learning, and about the principle of military oversight.



Near the end of the war, Stone participated in the creation of the “Jeffries Committee,” a group of  Met Lab scientists led by Zay Jeffries that produced a 65-page report detailing post-war applications for atomic science. Stone also served on a number of committees responsible for the post-war transformation of the Met Lab. These included the Lab Council, which took over for the discontinued Project Office, and the Committee on the Release of Scientific Information, which worked with Army representatives to determine how many of the scientists’ findings could be published.

Stone was also honored in the official press release that the University of Chicago put out about the university’s role in the atomic bombs’ creation. In 1946, he received the Medal of Merit for his wartime work from General Leslie R. Groves, equivalent to the modern Presidential Medal of Freedom.

He resigned from the Met Lab in February 1946, but remained a consultant. Leon Jacobson, his longtime deputy, replaced him as Health Division leader. He returned to San Francisco and to his post at department chairman. In 1951, he also became Director of UCSF’s Radiation Laboratory, holding both posts until his retirement in 1964. He served concurrently on numerous committees and boards related to radiology and radiation safety, including becoming president of the Radiation Society of North America.

His postwar research included using radiation therapy for arthritis patients. He also published a book on the Health Division’s research, in 1951. In 1949, Stone controversially advocated for radiation experiments involving healthy prisoners, but because of opposition from the Atomic Energy Commission, the experiments never came to pass. He was also known for being a strong advocate for patient consent. He died in San Francisco in 1966. 

Robert S. Stone's Timeline

  • 1895 Jun 5th Born in Chatham, Ontario, Canada.
  • 1928 Graduated with the last of his four degrees from the University of Toronto (his MD).
  • 1928 to 1964 Served on the faculty of the University of California, San Francisco (with a leave for the Manhattan Project work).

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