The effects of prior catecholamine reductions produced by 6-hydroxydopamine on the behavioral depressant effects of catecholamine depleting and neuroleptie drugs were examined using a continuously reinforced bar-press response. In spite of large depletions, 6-hydroxydopamine treated rats showed no deficits in performance. Similarly, animals preferentially depleted of norepinephrine or dopamine showed no deficit in this task. When a-methyltyrosine or reserpine were administered at a dose which had minimal effect on responding in control animals, the 6-hydroxydopamine group in which both amines were reduced and the group preferentially depleted of dopamine showed severe deficits in bar-press responding. Responding in rats preferentiaUy depleted of norepinephrine was slightly reduced but not to the extent observed in animals depleted of dopamine. Administration of the dopamine-fl-hydroxylase inhibitor, U-14,624, depressed responding but did not produce differential effects which correlated with brain norepinephrine concentration in the 6-hydroxydopamine-treated groups. Furthermore, the behavioral depression produced after treatment with chlorpromazine, haloperidol, and pimozide was not altered by any of the 6-hydroxydopamine treatments. These findings provide further evidence for the view that dopamine depletion plays a major role in the behavioral depressant effects of a-methyltyrosine and reserpine, but do not eliminate a role for brain norepinephrine.