While the debate raged, Pauling continued to keep a high public profile, speaking widely and appearing often in newspapers and magazines through 1956 and into 1957, garnering attention by positing shocking estimates of fallout-related damage to human health. By the spring of 1957 it appeared that his and Russell’s efforts were yielding fruit. Alarmed by the dangers of fallout, Japanese, British, German, and Indian politicians began urging a halt to H-bomb tests, as did the Pope and the World Council of Churches.

In May, after delivering a fiery anti-Bomb speech at Washington University in St. Louis, Pauling conferred with two other scientists, Barry Commoner and Edward Condon, about next steps. They decided to mount a scientists’ petition to stop nuclear testing as a way to draw attention to the concerns of a growing number of anti-Bomb scientists. Their "Appeal by American Scientists to the Government and Peoples of the World," mimeographed and hand-mailed, garnered more than two dozen signatures within a week. Pauling took the project back to Pasadena, where he and Ava Helen, along with some volunteers, mailed hundreds of additional copies to researchers in more American universities and national laboratories. Within a few weeks they had gathered some two thousand signatures, including more than fifty members of the National Academy of Sciences and a few Nobel laureates.

On June 3, Pauling released his signatures to the world, sending copies to the United Nations and President Eisenhower. The petition made national headlines -- and spurred an immediate attempt to isolate its primary author. Even the president took a shot at Pauling. "I noticed that in many instances scientists that seem to be out of their own field of competence are getting into this argument about bomb testing," said Eisenhower, "and it looks almost like an organized affair." This thinly veiled allusion to Communist backing for Pauling’s effort was echoed by a number of other critics of the ban-the-Bomb movement. The head of HUAC blasted Pauling on the floor of Congress for spreading Soviet propaganda. A few days later Pauling was subpoenaed to appear before a Senate investigatory committee (although those hearings were delayed, then canceled). Through it all, he continued to broaden the distribution of his petition through the end of 1957, expanding his mailing list to scientists around the world, including many in Communist countries. By the beginning of 1958, he and Ava Helen counted more than 9,000 signatures. When the expanded petition response was submitted to the United Nations, it once again made headlines worldwide.