We report the results of our study suggesting that a single dose pharmaco-EEG may predict treatment response to tetrahydroaminoacridine (THA) in Alzheimer's disease (AD). 14 AD patients and 7 age-matched neurologically healthy controls were selected for the study. AD patients had 7 weeks' THA treatment. 6 patients were regarded as responders and 8 patients as nonresponders, respectively. AD patients as well as controls had a baseline EEG recording and next day another recording 90 minutes after a peroral single dose of 50 mg THA. The relative change from the baseline in the alpha-theta ratio was the most sensitive discriminator of responders and nonresponders (P = 0.004, ANOVA).