This chapter examines assessment, treatment, and decision-making skills and discusses emergency levels and triage decisions, emergent nursing situations, and illicit and illegal drug emergencies. An emergency nurse is a nurse with specialized diagnostic and treatment skills in emergency nursing. This nurse has to be able to handle life-threatening emergencies and must be aware of a wide range of illnesses, injuries, treatments, medications, and complications. The nurse must also be knowledgeable in advanced monitoring and treatment equipment. Patient emergency levels are labeled as Priority Levels I, II, III, or IV based on their medical, psychological, community, and substance-abuse requirements. There may be patients who are admitted to the emergency room under the influence of illicit and illegal drugs. Drug screening should be done if there appears to be any changes in the patient’s mental status or trauma or injury.