Maternal deprivation has been shown to increase vulnerability to morphine dependence and to disturb the enkephalinergic system in adulthood. To study whether or not this vulnerability to opiates is a specific feature, we examined oral self-administration behaviour of various reinforcing substances. Experiments were performed with morphine (25 mg/l), ethanol (10%), amphetamine (25 mg/l) and cocaine (100 mg/l). Drugs were available in a continuous free choice paradigm during 3 months. Cocaine and ethanol consumption and preference were similar in both deprived and control rats. Deprived rats greatly increased their morphine consumption and 78% of them showed a progressive decrease in morphine aversion. Only a slight, but significant, increase in oral amphetamine consumption was observed in deprived rats when compared with control rats. The difference in amphetamine self-administration in control and deprived rats cannot be explained by a modification of dopamine transporter expression measured by immunoautoradiography. Altogether, we conclude that maternal deprivation worsens inherent susceptibility to dependence, specifically for opiates, and therefore represents a highly valuable model to study environmentally triggered interindividual vulnerability to opiate addiction.