Catecholamine levels and turnover have been analyzed in DA cell body and in terminal-rich areas of the midbrain, diencephalon, and forebrain 48 hr following a 2-week treatment with l-sulpiride and haloperidol. At this time interval behavioral supersensitivity to DA agonists has been demonstrated. No changes in DA turnover are found in the DA cell body groups A9 and A10 or in various DA terminals of forebrain, with a possible exception for the diffuse type of DA terminals in the tuberculum olfactorium where a reduction of DA turnover rate is observed. In the median eminence of the l-sulpiride-treated group, however, DA turnover increases are observed. It is suggested that the lack of amine turnover changes in most of the DA terminal systems of the brain is related to the development of DA receptor supersensitivity in both striatal and limbic areas, balancing the DA receptor blocking activity of the neuroleptic drugs still present in the tissue of the brain.