The inhibitory effects of (-)-epigallocatechin gallate (EGCG), a major compound of green tea, on the development of locomotor sensitization, conditioned place preference (CPP) and dopamine receptor supersensitivity induced by the repeated administration of morphine were investigated in mice. A single administration of morphine produces hyperlocomotion. The repeated administration of morphine develops sensitization, a progressive enhancement of locomotion, which is used as a model for studying the craving and drug-seeking behaviors characterizing addiction, and CPP, which is used as a model for studying drug reinforcement, respectively. EGCG inhibited morphine-induced hyperlocomotion, sensitization and CPP. In addition, EGCG inhibited the development of postsynaptic dopamine receptors supersensitivity, which may be an underlying common mechanism that mediates the morphine-induced dopaminergic behaviors such as sensitization and CPP. Apomorphine (a dopamine agonist)-induced climbing behaviors also were inhibited by a single direct administration of EGCG These results provide evidence that EGCG has anti-dopaminergic activity, as inhibiting the development of dopamine receptor supersensitivity and apomorphine-induced climbing behaviors. Therefore, it is suggested that green tea may be useful for the prevention and therapy of these adverse actions of morphine.