Through her constant efforts of public awareness, she was able to galvanize others into action. What began as a letter written to a newspaper later resulted in the Australian government contesting the French in the International Court of Justice. The Court's decision ultimately led to a ban on nuclear atmospheric testing in the Pacific Ocean.
In the late 1970s Dr. Caldicott moved to Boston, Massachusetts to teach at Harvard University. There she became co-founder of the Physicians for Social Responsibility. Initially consisting of only 10 members in 1979, the organization has since grown and evolved into the International Physicians for the Prevention of Nuclear War (IPPNW). With over 135,000 concerned medical professionals and citizens, the organization has educated countless people about the effects of nuclear war. In 1985 the Nobel Peace Prize was presented to the IPPNW for their role in peace education. The Nobel Committee announced that "the organization has performed a considerable service to mankind by spreading authoritative information and by creating awareness of the catastrophic consequences of atomic warfare."
Her peace activism has continued over the years. Besides being the inspiration for the IPPNW, she founded the Women's Action for Nuclear Disarmament and has served as the Director of the Stanley Foster Foundation, an organization dedicated to the promotion of environmental education.