During the 1990s, Johnson and several others challenged the scientific consensus by claiming that HIV tests do not detect HIV, AIDS statistics are grossly exaggerated, and that HIV is not the cause of AIDS. As a member of The Group for the Scientific Reappraisal of the HIV/AIDS Hypothesis, a prominent AIDS denialist group, Johnson questioned if HIV caused AIDS. He wrote several articles about the subject, including a piece in "Reason" magazine. He was one of the 12 founding members of The Group for the Scientific Reappraisal of the HIV/AIDS Hypothesis and signatory to the group's letter to the editor of "Science" asserting that HIV is only tautologically associated with AIDS and that HIV tests are inaccurate.