The third edition of The American Society of Addiction Medicine Handbook of Addiction Medicine provides authoritative, evidence-based guidance on evaluating, treating, and managing patients with substance use disorders. It begins with a clinical perspective on addiction, followed by an overview of treatment modalities and strategies for effective patient engagement. The handbook includes eight detailed chapters on specific drug classes: alcohol, sedatives, opioids, nicotine, stimulants, cannabinoids, hallucinogens, and inhalants, each covering diagnosis, medical complications, and treatment.Additional chapters address the non-medical use of prescription drugs, anabolic steroids, and athletes. It also covers comprehensive medical care for patients with substance use disorders, including primary care, complications from injection drug use, harm reduction, care of patients receiving opioid agonist treatment, and pain management. Guidance on assessing and treating psychiatric disorders in patients with substance use disorders is provided, along with discussions on the impact on special populations such as adolescents, women, older adults, LGBTQ individuals, and health professionals. The final chapter explores ethical and legal considerations, including the criminalization of drug use, Good Samaritan laws, the Americans with Disabilities Act, substance use during pregnancy, and core clinical ethical principles.