It has been suggested that high levels of behavioral approach system (BAS) sensitivity predispose psychopathological conditions that are characterized by a pathological engagement in approach behaviors, such as alcohol and drug abuse. The present study examined differences in scores on the BIS/BAS scales between clinically referred drug addicts and alcoholics and healthy control subjects. Results showed that drug addicts had higher BAS scores than controls and this was particularly true for BAS drive and BAS fun seeking. No differences were observed between the alcoholics and the other two groups. This is the first time that a relation between heightened BAS and drug addicts is observed in a clinical sample. These findings provide partial support for Gray's personality theory, which predicts a relation between BAS and substance abuse.