Many adolescents and young adults engage in drinking behaviour, which result in acute and chronic negative consequences (eg: unintentional injuries, arguments, unplanned and/or unprotected sexual activities, trouble with police/authorities, poor academic/work performance, suicide, and death), and alcohol dependence. Social influence is foremost among the causes attributed to the initiation and maintenance of alcohol use during this period. This book reviews a number of prominent theories of social influence that are directly relevant to drinking behaviour among adolescents and young adults.