To determine if the pattern of cognitive decline in Alzheimer's disease (AD) patients with normal EEG differs from that in patients with abnormal EEG at the early stage of the disease, we have followed 12 AD patients with normal EEG (NEEG) and 12 patients with deteriorating EEG (DEEG). The AD patients with DEEG showed a decline of praxic functions, confrontation naming, and automatic speech functions. In contrast, the AD patients with NEEG did not show a deterioration of these functions during the 3-year follow-up period. Visual functions, understanding of speech, and memory functions deteriorated similarly in both groups. The clinical severity of dementia increased in both groups. Patients with DEEG showed a tendency toward a higher frequency of extrapyramidal symptoms and a higher risk of institutionalization than the patients with NEEG. Thus, an abnormal EEG at the early stage of AD may predict a more severe decline in cognitive functions.