The authors conducted a study in which schizophrenic-like behavioral disturbances were induced in members of a macaque social colony by the chronic administration of d-amphetamine. Animals given the drug showed hypervigilance, hyperactivity, fragmented and repetitive behaviors, and progressive social withdrawal as well as the development of solitary stereotypies. The syndrome was dissected pharmacologically with alpha-methyl-para-tyrosine, chlorpromazine, pimozide, and haloperidol. Based on the behavioral findings and the known mechanisms of action of these drugs, the authors conclude that the major elements of the psychotic-like behavior induced by d-amphetamine were mediated by dopamine systems.