The importance of a comprehensive and holistic sexuality education has been presented and discussed in the last few years in several international documents. Key arguments of this discussion and the content and methods to deliver sexuality education will be presented here. The focus is on Finland, the only country where the content and progress of sexuality education has been studied in consecutive national surveys directed at teachers and by measuring adolescents' sexual knowledge at a national level. A special focus in this chapter is teenage boys' sexuality education. The BoyS Project has studied the sexuality-related issues that occupy boys' minds, the kind of sexuality education they would like to receive, and has also produced a guide for educators, video clips for educators and boys, and the Superstud mobile game that educates boys about sexuality. Adolescent sexuality and adolescents' sexuality education has not often been studied from boys' point of view. It is important to gain a deep understanding of boys' needs, since sexuality education has been found in some western countries to be more important in determining sexual health knowledge among boys than girls. The BoyS Project, which commenced in 2011, was conceived to improve sexual knowledge among adolescent boys. The data includes 60 personal interviews, 10 focus group interviews, 53 essays, 520 questions submitted to a sexual counseling website called "Ask the Expert", and thousands of calls made to a boys' telephone helpline. The telephone helpline data includes crisis calls related to boys' problems with sexuality. The results of the BoyS Project data include several themes. Among these are boys' concerns and worry about whether they are maturing properly. They want a prognosis of whether they are going to be physically "normal." The greatest concern and cause for anxiety is the size and function of their penis. They are afraid that their penis is not functional enough to give pleasure to girls. They also crave information about how to behave in sexual intercourse. They are afraid to reveal their ignorance and inexperience, especially in the classroom. When commenting on sexuality education, boys do not consider classroom sexuality education to be believable and worth listening to if it contains mainly lectures about sexual risks. The same is true if they are spoken to in an accusatory manner about their interest in pornography. Boys want to become sexually active and to earn the role of a hero among other boys. Sexuality education should be able to simulate situations that are as authentic as possible and to reflect the kinds of events that actually take place in boys' lives. The challenge is finding ways to bring these real-life situations into the classroom in a way that seems both authentic and credible to students, without any labels or embarrassment.