[1][2][3] Warren influenced and mentored Eleanor Josephine Macdonald, epidemiologist and cancer researcher.

[5] From 1923 to 1925, he was an assistant in pathology at Boston City Hospital where he completed his medical residency in 1927.

[6] He held the Shields Warren Mallinckrodt Professorship of Clinical Research at Deaconess Hospital and Harvard Medical School Warren's research focused primarily on cancer, thyroid disorders, diabetes, and atomic radiation.

He also helped to establish the field of radiobiology by determining that certain mammal tissues were more susceptible to radiation damage, therefore disproving the Law of Bergonie and Tribondeau.

[8]Warren's various research projects involved the American Society for Experimental Pathology, the U.S. Atomic Energy Commission, the U.S. Department of Defense, the National Academy of Sciences, NASA, and the Veterans' Administration.