The authors examined the presence of significant regional cerebral blood flow (rCBF) differences between Alzheimer's disease (AD) patients with and without extrapyramidal signs (EPS). Nine patients with probable AD and EPS (resting tremor or rigidity and bradykinesia) and 9 AD patients without EPS, comparable in age, duration of illness, and global cognitive decline, were studied with [99mTc]HMPAO SPECT. Patients with AD and EPS showed significantly lower rCBF in the superior frontal, superior temporal, and parietal regions of the left hemisphere than AD patients without EPS. Rigidity and bradykinesia independently accounted for the decreased rCBF in these areas. These findings suggest that the presence of EPS in AD may result from dysfunction in specific brain regions.