We measured the concentrations of dopamine, 3, 4-dihydroxyphenylacetic acid, and homovanillic acid in several cortical areas from controls and parkinsonian patients. Substantial amounts of dopamine and its metabolites were detected in hippocampus and endocrinal, cingulate, and frontal cortex of controls. In parkinsonian patients the levels of dopamine and its metabolites were reduced in these neo-cortical areas and hippocampus. Diminution of cortical dopaminergic transmission may play a role in the mental impairment of some Parkinson patients.