Drug addiction is a complex brain disorder characterized by compulsion to seeking and taking drugs despite severe consequences to health and social relationships. One feature of addiction is that it accompanies exposure to drugs having different pharmacological mechanisms. One of the most interesting hypothesis proposed in recent years, is that neuronal processes thought to form the cellular basis for learning (e.g. long-term potentiation, LTP) may occur in the mesolimbic reward system after drug exposure. This review describes briefl y behavioral processes underlying drug addiction (particularly the behavioral sensitization) and examines the processes ( such as glutaminianergic transmission, LTP formation and protein synthesis) underlying memory consolidation and reconsolidation. Theoretically, new fi ndings on memory have implication for treatment of drug addiction. For example, pathological drug-related memories may be disrupted after their acquisition and consolidation by impairing their reconsolidation after retrieval.