This article discusses basic concepts of sexuality in children, adolescents, and young adults based on development stages. Sexual behavior of adolescents is a common phenomenon, leading to sexually transmitted diseases (STDs) and unwanted pregnancy. Clinicians should provide anticipatory guidance to help with healthy sexuality development while reducing negative aspects of human sexuality. Comprehensive sexuality education should be provided, with emphasis on avoiding unwanted sexual advances (including Internet dangers), bullying, pregnancy, and STDs. Clinicians can teach sexually active patients to use effective contraception and condoms for STD protection. Ensuring full immunization with the hepatitis B vaccine and the human papillomavirus vaccine also is important.