AbstractKey points are highlighted from five papers that address biological processes underlying the actions of opiates, CNS stimulants, nicotine, alcohol, and benzodiazepines. It is noteworthy that: (1) positive and negative reinforcement are common processes underlying actions of drugs of dependence; (2) dopaminergic systems in the ventral tegmental area of the brain seem to be involved in the positive reinforcement of drugs of dependence; (3) GABA also may be involved in this positive reinforcement; (4) receptor sensitization and desensitization may be involved in the actions of drugs of dependence; (5) noradrenalin, 5–HT, ACh, NMDA and corticosteroids also may be involved in drug dependence; (6) motivational systems and processes in addition to positive and negative reinforcement deserve increased research attention; and (7) there may be genetic–based individual differences in drug dependence proces