Adolescent substance abuse, with its heterogeneity, its complexity and its association with behavioural, physical and mental health problems is of increasing interest to many; the politician, the economist, clinicians and researchers, families and young people themselves. Data concerning the prevalence and trends in use of a range of substances in different countries, cultures and different groups are reviewed. The influence of associated mental and physical health problems, the multiple definitions applied to use and abuse and the confounding effect of different ideologies and cultural differences are considered. There is now much interest in the understanding of risk and protective influences, including multi focused prevention programmes among vulnerable young people. Some positive effects of universal prevention programmes are reported, although too often they lack thoroughness in programme implementation, data collection and follow up. Indeed compared to the adult addiction literature there is a death of research on adolescent treatment outcomes. Research needs to address treatment and cost effectiveness in different settings with different groups. The evidence tends to support multi faceted interventions for high risk youths. However, the use of evidence based programmes with a scientific basis should be supported and implemented.