Administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to primates produces many of the biochemical, morphological and behavioral changes that occur in Parkinson's disease. MPTP-induced degeneration of the mesostriatal dopamine innervation has been well documented. In the present study, concentrations of dopamine and norepinephrine in cortical regions surrounding the cingulate sulcus were assessed, and were found to be markedly decreased in symptomatic MPTP-treated vervet monkeys; these results parallel the cortical involvement in Parkinson's disease. Dopamine and norepinephrine levels were not reduced in a group of asymptomatic MPTP-treated monkeys that suffered large losses of striatal dopamine concentration. If therefore appears that the dopaminergic innervations of the supplementary motor area and cingulate cortex are susceptible to MPTP-induced degeneration, but are less vulnerable than the striatal dopamine innervation.