Striatal dopamine reuptake sites were studied with PET in Alzheimer's disease (AD). A cocaine analogue, [11C]beta-CFT was used as a radioligand. In patients with AD, the reduction in [11C]beta-CFT uptake was about 20% from the age-adjusted mean value in control subjects, both in the putamen (p = 0.002) and in the caudate nucleus (p = 0.002). Thus, the putamen and the caudate nucleus were equally affected, in contrast to Parkinson's disease, which shows predominantly putaminal reduction. We found that the smaller the [11C]beta-CFT uptake in the putamen or in the caudate nucleus, the more severe the extrapyramidal symptoms. In healthy volunteers (nine women, six men; aged 23 to 70 years), [11C]beta-CFT uptake was reduced with age, both in the putamen (r = -0.70, p < 0.01) and in the caudate nucleus (r = -0.77, p < 0.001). The average decline per decade was 4.4% in the putamen and 4.7% in the caudate nucleus. We conclude that the brain dopaminergic system is affected in AD because the striatal uptake of the dopamine reuptake ligand [11C]beta-CFT is decreased. This reduction in [11C]beta-CFT uptake correlates with the severity of the extrapyramidal symptoms of the patients.