Operation Sore Throat was a major campaign mounted against the American Medical Association. Several Scientologist agents were infiltrated into the AMA as employees, one of whom gained access to meetings of the AMA's board of directors. In June 1975, the AMA found itself repeatedly embarrassed by leaks of confidential documents to the press by an unknown source who called himself "Sore Throat" – a punning reference Deep Throat of Watergate scandal fame. The documents disclosed the AMA's political activities and liaison with the pharmaceutical industry, including lobbying for nominees to federal appointments and details of financial transactions between drug companies and the AMA's political arm.
"Sore Throat" claimed to be "a doctor who worked in the A.M.A.'s Chicago office for about ten years" who had become discontent with the AMA's policies and moved to Washington, DC. In reality, he was Scientologist agent Michael Meisner, who was later to be a key witness for the US Government against the Guardian's Office leadership.
The leaks led to the AMA being investigated by the Internal Revenue Service, the US Postal Service, a number of Congressional committees, Ralph Nader and the press. The AMA's internal leak investigation ultimately pointed to the Church of Scientology being behind the leaks. A GO memorandum of May 16, 1977 explained the circumstances of the investigation: "3 agents got placed in 2 AMA offices. It fell apart in Oct. '75 when the DC missionaire [sic] leaked data to the press which identified one of the agents. The AMA called in a firm of investigators who blew the Chicago agent ... and then traced a connection to the DC agents."
Two secretaries in the AMA's Washington office were discovered to be Scientologists, one working under an assumed name. Sherry Canavarro, a secretary in the AMA's Chicago office, was also found to be a Scientologist and was given a lie detector test. Although she passed, confidential minutes from the AMA's board of directors were found in her desk and she was determined to have spent several unexplained weekends at work. She subsequently resigned. When the FBI investigated the case, it discovered that Canavarro also used the names "Sherry Hermann" and "Sandy Cooper" and held the post of Pacific Secretary of the Guardian Office United States. Although Canavarro escaped legal charges, her husband Mitchell Hermann was subsequently convicted on conspiracy charges and was imprisoned.
Operation Sore Throat was masterminded at a high level within the Guardian's Office, as the US Government's sentencing memorandum in United States of America v. Jane Kember, Morris Budlong documented. Kember, the Guardian Worldwide, sent a cover story to Deputy Guardian US Henning Heldt: "David [Gaiman] has laid down a strategy which is to enable us to contain the scene. Our plants when trapped are Freedom investigative reporters just like any other newspaper. The plants themselves do not have to confess or be named ... We can undercut AMA's continual effort to expose us by indicating it is a smokescreen to prevent Freedom from publishing."
The AMA accused the Church of Scientology of being behind "Sore Throat" but Scientology spokesman denied responsibility, accusing the AMA of "grasping in the dark to cover their own crimes." Even after the GO's role was exposed, Scientology spokesmen defended the leaker's actions: ""Whoever 'Sore Throat' was should get a medal," Jeffery Dubron told the Los Angeles Times. "I don't know who that person was ... If this person went in and lied to get a job in the AMA and exposed crimes and created change, should that person be prosecuted for his or her actions?"
In addition to the "Sore Throat" campaign, the GO carried out a series of burglaries of law firms working for the AMA. The offices of law firms Sidley & Austin were burgled by two Scientologists in 1976 who copied legally sensitive AMA files after carrying out a 90-minute search.