Commencing in 1983, the Australian Temperament Project (ATP) is now in its 25th year and has competed 14 data collection waves. This project provides a unique lens through which to view the pathways to vulnerability and resilience at Australian children from infancy to adolescence and beyond. This chapter provides an overview of the study findings on adolescent antisocial behaviour, substance use, internalising problems and aspects of positive development and well-being. Several pathways to vulnerability or resilience are described that vary in their age of onset. Constellations of common risk factors suggest that there may be overlapping priming factors for later mental health problems. A different mix of factors relate to pathways to well-being. This unique Australian study provides invaluable insights into stability and change in the pathways to mental health that children take across life.