Young people are taking part in a wider range of sexual practices, including anal sex, with opposite sex partners, research reveals.
Experts looked at responses to a national sex survey that has been carried out every 10 years since 1990 in the UK.
More than one in 10 millennial teenagers said they had tried anal sex by the age of 18.
By the age of 22 to 24, three in every 10 said they had tried it.
Vaginal and oral sex are still the most common types of sexual activity between young men and women, however.
The age that young people start having sex - vaginal, anal or oral - has not changed much in recent decades.
In the most recent survey, it was 16.
While the study in the Journal of Adolescent Health shows what types of sex people are having, it doesn't shed light on why preferences are changing.
Experts can only speculate, but say society has become more accepting and less judgemental about sexual experimentation.
