In a candid confession, the Basic Instinct star said he was told his throat cancer was triggered after he contracted the human papillomavirus (HPV) - the most common form of sexually transmitted disease.
It had been widely thought the 68-year-old Hollywood star’s years of drinking and smoking were to blame for the stage four cancer, which was first diagnosed in 2010.
But in a new interview Douglas - married since 2000 to British actress Catherine Zeta Jones, 43 - said oral sex had caused the disease.
Asked if he now regretted his years of smoking and drinking, he replied: “No. Because without wanting to get too specific, this particular cancer is caused by HPV, which actually comes about from cunnilingus.”
He went on to say that oral sex was also the best cure - a claim doctors deny.
He lost more than 45lbs following chemotherapy and radiation treatment - but has been cancer-free for two years.