Levels of iron, copper, zinc, manganese, and lead were measured by inductively coupled plasma spectroscopy in parkinsonian and age-matched control brain tissue. There was 31-35% increase in the total iron content of the parkinsonian substantia nigra when compared to control tissue. In contrast, in the globus pallidus total iron levels were decreased by 29% in Parkinson's disease. There was no change in the total iron levels in any other region of the parkinsonian brain. Total copper levels were reduced by 34-45% in the substantia nigra in Parkinson's disease; no difference was found in the other brain areas examined. Zinc levels were increased in substantia nigra in Parkinson's disease by 50-54%, and the zinc content of the caudate nucleus and lateral putamen was also raised by 18-35%. Levels of manganese and lead were unchanged in all areas of the parkinsonian brain studied when compared to control brains, except for a small decrease (20%) in manganese content of the medial putamen. Increased levels of total iron in the substantia nigra may cause the excessive formation of toxic oxygen radicals, leading to dopamine cell death.