Michael Douglas has made a jaw-dropping revelation about the cause of his throat cancer.

The Oscar-winning actor told The Guardian newspaper he didn't contract it from smoking or drinking, but from oral sex.

Douglas said he contracted HPV, or human papillomavirus, from a sex act, which developed into cancer.

"Without wanting to get too specific, this particular cancer is caused by HPV, which actually comes about from cunnilingus," he told the British newspaper in an interview published Sunday.

Shortly after being diagnosed in 2010, Douglas said the kind of cancer he had was caused by smoking and drinking.

But now, the 68-year-old actor also wonders if the stress caused by his son Cameron's legal woes didn't play some part as well.

"I did worry if the stress caused by my son’s incarceration didn’t help trigger it," Douglas said of his son, who is serving 10 years in a federal prison for heroin possession and distribution.

"But, yeah, it’s a sexually transmitted disease that causes [the] cancer."