Let's face it, most of us were too busy laughing at our teacher putting a condom on a banana to pay that much attention in sex ed at school.
So as adults, sometimes we're not as clued up about safe sex and STIs as we like to think we are.
This year, Sexual Health Week, ran by the Family Planning Association, is focussing sexually transmitted infections (STIs), which includes knowing the facts when it comes to safe sex.
Test how good your knowledge is by taking the online sexual health quiz below created by NHS Choices.
The test will highlight any areas where your knowledge might be lacking, then give advice on what to do if you think you may be at risk of having an STI, or if you have an unwanted pregnancy.