Since winning the Nobel Prize, Mullis has been criticized in The New York Times for promoting ideas in areas in which he has no expertise. He has promoted AIDS denialism, climate change denial and his belief in astrology.
In his 1998 autobiography, Mullis expressed disagreement with the scientific evidence supporting climate change and ozone depletion, the evidence that HIV causes AIDS, and asserted his belief in astrology. Mullis claims climate change and the HIV/AIDS connection are due to a conspiracy of environmentalists, government agencies and scientists attempting to preserve their careers and earn money, rather than scientific evidence. Mullis has drawn controversy for his association with prominent AIDS denialist Peter Duesberg, claiming that AIDS is an arbitrary diagnosis only used when HIV antibodies are found in a patient's blood. The medical and scientific consensus is that Duesberg's hypothesis is pseudoscience, HIV having been conclusively proven to be the cause of AIDS and that global warming is occurring because of human activities. Seth Kalichman, AIDS researcher and author of Denying AIDS, "[admits] that it seems odd to include a Nobel Laureate among the who's who of AIDS pseudoscientists". Mullis also wrote the foreword to the book What If Everything You Thought You Knew About AIDS Was Wrong? by Christine Maggiore, an HIV-positive AIDS denialist who, along with her daughter, died of an AIDS-related illness. A New York Times article listed Mullis as one of several scientists who, after success in their area of research, go on to make unfounded, sometimes bizarre statements in other areas. An article in the Skeptical Inquirer described Mullis as an "...AIDS denialist with scientific credentials [who] has never done any scientific research on HIV or AIDS". Use of LSD
Mullis details his experiences synthesizing and testing various psychedelic amphetamines and a difficult trip on DET in his autobiography. In a Q&A interview published in the September, 1994, issue of California Monthly, Mullis said, "Back in the 1960s and early '70s I took plenty of LSD. A lot of people were doing that in Berkeley back then. And I found it to be a mind-opening experience. It was certainly much more important than any courses I ever took." During a symposium held for centenarian Albert Hofmann, "Hofmann revealed that he was told by Nobel-prize-winning chemist Kary Mullis that LSD had helped him develop the polymerase chain reaction that helps amplify specific DNA sequences." Replying to his own postulate during an interview for BBC's Psychedelic Science documentary, "What if I had not taken LSD ever; would I have still invented PCR?" He replied, "I don't know. I doubt it. I seriously doubt it." Extraterrestrial life
Mullis writes of having once spoken to a glowing green raccoon. Mullis arrived at his cabin in the woods of northern California around midnight one night in 1985, and, having turned on the lights and left sacks of groceries on the floor, set off for the outhouse with a flashlight. "On the way, he saw something glowing under a fir tree. Shining the flashlight on this glow, it seemed to be a raccoon with little black eyes. The raccoon spoke, saying, ‘Good evening, doctor,’ and he replied with a hello." Mullis later speculated that the raccoon ‘was some sort of holographic projection and … that multidimensional physics on a macroscopic scale may be responsible’. Mullis denies LSD having anything at all to do with this.