Drug addiction is a brain disorder caused by the repetitive use of various chemicals which alter normal functioning of the central nervous system with consequent behavioral abnormalities. In the search to understand which neurotransmitter systems play upon this behavioral pathology, dopamine has long been thought to play a prima donna role. However, its primary role is commonly and erroneously attributed to the increase in activity after acute administration of addicting drugs. On the contrary, the mesolimbic dopamine transmission appears to be drastically reduced in its tonic activity when measured in animal models, which mimic the human condition of drug addiction, and in the available human studies conducted in addicted subjects. This paper is a systematic review of the pertinent literature which strongly supports this concept. Various