This guidebook sets out the public health rationale for making it easier for adolescents to obtain the health services that they need to protect and improve their health and well-being, including sexual and reproductive health services. It defines ‘adolescent-friendly health services’ from the perspective of quality, and provides step-by-step guidance on developing quality standards for health service provision to adolescents. Drawing upon international experience, it is also tailored to national epidemiological, social, cultural and economic realities, and provides guidance on identifying what actions need to be taken to assess whether appropriate standards have been achieved.