Postmortem studies in neuropsychiatric disorders test hypotheses with regard to schizophrenia, suicide, and addictions. New findings in schizophrenia include the following: (1) decreased ketanserin binding (serotonin-type 2 receptors) in frontal pole, dorsolateral cortex and cingulate cortex in schizophrenics and schizoaffectives relative to controls; (2) decreased paroxetine binding (serotonin reuptake site) in frontal pole and cingulate cortex in schizophrenics relative to controls; (3) normal glutamate binding in caudate nucleus and frontal cortex of schizophrenics versus controls; (4) normal 5HT-3 receptors in amygdala of schizophrenics. Structural abnormalities have focused on the parahippocampal gyrus which is reduced in size bilaterally in schizophrenia and on the right side in suicides. New findings in affective disorders and suicide brains in frontal cortex include decreased ketanserin binding in schizoaffectives and increased ketanserin binding in non-psychotic suicides. Paroxetine binding in frontal cortex is normal in schizoaffectives and decreased in suicides. In addition, alterations in pineal melatonin, serotonin, and 5HIAA rhythms were found in schizophrenics and suicide. Assays of postsynaptic serotonin receptors (ketanserin binding) and presynaptic serotonin receptors (paroxetine binding) in frontal cortex appear to allow to us to discriminate schizophrenics (down in both) from schizoaffectives (down in ketanserin only) and non-psychotic suicides (up in ketanserin, down in paroxetine). Findings in additions include decreased paroxetive binding in hippocampus of alcoholics and normal PCP and sigma receptors in PCP users in multiple brain regions.