First published in 1991, the SIECUS guidelines have been translated into several languages and adapted in many countries. They were the first national model for comprehensive sexuality education in the United States. Established by a taskforce of experts, they provide a framework for educators to create new sexuality education programmes and evaluate existing curricula. They define concepts, topics, skills and messages that should be at the core of sexuality education courses and explain at which age level information should be introduced. The guidelines have been regularly updated since 1991 to adapt messages and age levels to scientific and cultural changes. The guidelines are designed to be adaptable to the needs and beliefs of different communities. They are based on SIECUS' belief that everyone has a right to comprehensive sexuality education, the primary goal of which is to: help young people develop a positive view of sexuality, "provide them with information they need to take care of their sexual health, and help them acquire skills to make decisions now and in the future". The purpose of this document is to assist educators in evaluating existing sexuality education programmes or developing new ones. The guidelines provide key concepts, topics and messages that these programmes should include. The document includes: an introductory chapter presenting the history, structure, goals, values and fundamental principles of the guidelines; a core chapter detailing the six key concepts (human development, relationships, personal skills, sexual behaviour, sexual health, society and culture), topics and sub-concepts, as well as age-appropriate developmental messages for each; a chapter on how to use the guidelines providing advice on curricula evaluation and how to prioritise learning objectives; a comprehensive list of useful US websites on sexuality, HIV and sexually transmitted infections (STIs) and sex education.