Since changes of levels of biogenic amines have been found in some brain areas of rats bearing the Walker-256 tumor, a study was performed to assess the actions of three anorectic agents in such animals. The results obtained by dosage of d-amphetamine, fenfluramine or mazindol, on days 5 and 8 after tumor implantation, failed to demonstrate conclusively any predominant modification of a dopaminergic, noradrenergic, or serotonergic system in the anorectic effects of these agents.