This document defines and compares substance dependence, abuse, intoxication, and withdrawal according to the DSM-IV and ICD-10 diagnostic criteria. Substance dependence involves a maladaptive pattern of use leading to behaviors, cognition, and physiology after repeated intake and reliance on the substance. Substance abuse also involves maladaptive use but is defined by recurrent adverse consequences from misuse. Both can involve compulsive use, tolerance, and withdrawal symptoms. Substance intoxication and withdrawal are also defined based on their physiological and psychological effects.