Healthcare improvements leading to decreased infant and childhood mortality has given rise to the largest generation of adolescents in human history. An estimated 90% of adolescents in the world today live in low and middle income countries. In this presentation, Prof Patton speaks about the changes in adolescent development and health needs which, in turn, influence the changing platforms, particularly protective systems and health interventions. Poor and socially marginalized adolescents have the worst health profiles.. It is during adolescence that the risks for injury and mental illness are highest. Modifiable risk behaviors for later life non-communicable diseases (e.g. smoking, obesity and inactivity), are often formed in adolescence. Public health policies should identify priority programs for intervention and implementation at both national and local levels to improve adolescent health.