This research report focuses on the extent and impact of substance use and abuse among high school learners in Gauteng. The research results presented in this report were collected from randomly selected secondary schools in Gauteng, where 4,346 learners completed self-administered paper-based questionnaires during school time, in the presence of teachers and trained Youth Research Unit staff members. The research findings show that drug and alcohol abuse among young people is a reality with concerning consequences. Not only do young people find themselves in an environment in which drugs and alcohol are readily accessible, but very often these substances are used by their peers, to whom they relate and with whom they interact. Hence, their receptiveness to drug and alcohol use increases. Despite a general increase in cigarette smoking and the use of hubbly bubblies among young people, the research findings show the most common illicit drug used among learners, mainly for enjoyment and stress relief, is cannabis (dagga). A few learners reported the use of drugs to enhance performance at school, which clearly demonstrates the stress these learners experience and a desperate need for enhanced performance. It is noteworthy that learners often use drugs at home and school, both environments with a significant adult presence.