Around 20% of Britons aged between 16 and 24 claim to have had sex with at least one new partner while on holiday, new research shows.
A random sample of 12,000 men and women aged 16 to 44 who took part in the 2000 National Survey of Sexual Attitudes and Lifestyles were interviewed again for the study.
The respondents said North America, Thailand and Kenya are "high risk" areas for HIV infection.
They told researchers that choosing a British or European partner reduced the chances of HIV infection.
However, the young people appear to unaware of the risk of picking up other sexually transmitted diseases.
The Centre for Sexual Health and HIV Research at University College London conducted the study, which is published in the journal Sexually Transmitted Infections.
The authors wrote: "A substantial minority of young, unmarried people form new sexual partnerships abroad.
"Those who have new partners abroad are likely to have higher-risk sexual lifestyles more generally, and to be at higher risk of sexually transmitted infections.
"Greater attention should be paid to sexual health promotion for travellers abroad, especially young travellers, emphasising the risks of new sexual relationships with compatriots as well as those from other countries."