Introduction There have been numerous investigations linking some of the better known central aromatic amines with the actions of various types of psychoactive drugs. Seldom, however, have objective behavioral data and detailed chemical measurements been carried out in the same laboratory. Aprison and Ferster1 attempted to correlate brain monoamine oxidase activity with pecking behavior in pigeons, and Weissman and Finger2 studied the effect of benzquinamide on both conditioned avoidance behavior and brain amine levels in rats and monkeys. Often in correlative drug-behavior studies, such as these, only one central amine has been measured. It may well be that the balance between the amines rather than the absolute level of any one amine is the more important to behavior. In order to provide more precise information regarding central amine levels and behavior, we undertook the measurement of serotonin, norepinephrine, and dopamine in 16 brain areas from cats treated with