It is still unclear whether apolipoprotein E epsilon 4 (APOE E4) influences the cerebral glucose metabolism abnormalities found in Alzheimer's disease (AD), although APOE E4 is a well-known risk factor for AD. [(18)F]Fluorodeoxyglucose PET was conducted in patients with very mild (n=17), mild (n=27), and moderate-to-severe (n=19) AD. The presence of APOE E4 was associated with greater reduction of glucose metabolism in the left inferior temporal region in very mild AD but neither in mild nor in moderate-to-severe AD. These findings favor the hypothesis that APOE E4 is related mainly to the development of AD, not to its progression.