This chapter examines the effects of alcohol and provides a set of related definitions. The costs of excessive alcohol use are discussed, followed by a review of fundamental assessment and diagnostic procedures. Treatment approaches are a major focus, with an emphasis on evidence-based medications, behavioral interventions, and treatment models. The importance of support services for those struggling with alcohol addiction is stressed. This chapter concludes with resources that clinicians and clients can easily access in order to gain additional information on alcohol, its effects, its dangers, and treatment approaches.