The 68-year-old actor was diagnosed with throat cancer in 2010. In a recent interview published in the Guardian newspaper, Douglas said, "Because without wanting to get too specific, this particular cancer is caused by HPV, which actually comes about from cunnilingus."
The actor's spokesman, Allen Burry, said Douglas was not saying oral sex was the cause of his cancer - just that it was one of the many causes.
"In a discussion with the newspaper, they talked about the causes of oral cancer, one of which was oral sex, which is noted and has been known for a while now," Burry said.
Health officials say smoking and drinking alcohol are the main causes of oral cancer. But when it comes to oropharyngeal cancer, which is one kind of throat cancer, about 63 percent of the estimated 11,726 cases diagnosed each year in the U.S. are believed to be caused by HPV, according to the Centers for Disease Control and Prevention.
The Guardian also quoted Douglas saying he didn't regret his years of smoking and drinking. A spokesman for the newspaper told The Associated Press that they hadn't received any complaints about its interview either from Douglas or his representatives.
HPV is mostly known for causing cervical cancer. The virus is spread through oral, vaginal and anal intimacy, as well as through cunnilingus and fellatio.
ABC News and The Associated Press contributed to this report.