Evidence of an association between use of illicit substances and aggressive behavior is pervasive. But the precise causal mechanisms by which aggression is influenced by intoxicants are still not well understood. Research on intoxication and aggression often has overlooked the nonviolent behavior of most substance users, controlled use of substances, and the evidence from other cultures of a weak or nonexistent relation between substance use and aggression. There is only limited evidence that ingestion of substances is a direct, pharmacological cause of aggression. The temporal order of substance use and aggression does not indicate a causal role for intoxicants. Research on the nexus between substance use and aggression consistently has found a complex relation, mediated by the type of substance and its psychoactive effects, personality factors and the expected effects of substances, situational factors in the immediate settings where substances are used, and sociocultural factors that channel the arousal effects of substances into behaviors that may include aggression. Contemporary explanations of the intoxication-aggression relation offer only limited explanatory power in view of the occurrence of controlled use of substances, the mutability of cultural norms, and cross-cultural differences. Among contemporary explanations of violence and aggression, few have been more enduring than the presumed effects of intoxication from drugs or alcohol. There is pervasive evidence of an association between substance use and aggressive behavior. For example, drug abuse has been found to be a critical factor in homicide (Wolfgang and