Evidence from lesioning studies and neuroimaging has linked negative symptoms to dysfunction of the prefrontal cortex, the limbic system, and the basal ganglia. Although such symptoms have been most strongly associated with dopaminergic hypoactivity in the prefrontal cortex, other neurotransmitters including norepinephrine, serotonin, and the excitatory amino acids may also play a role. In some patients moderate doses of conventional neuroleptics clearly improve negative symptoms; the response of such symptoms is relatively greater with clozapine and probably with certain serotonin-dopamine antagonists. Recent studies demonstrating improvement of negative symptoms when conventional neuroleptics are augmented with selective serotonin-reuptake inhibitors or with agents active at the glycine-modulatory site of the glutamatergic N-methyl-D-aspartate receptor complex suggest that further amelioration of primary negative symptoms may be possible through pharmacological strategies involving multiple neurotransmitter systems.