Previous investigations have indicated that a single dose pharmaco-EEG may predict the outcome of 4-7 weeks of tetrahydroaminoacridine (THA) treatment in dementia of the Alzheimer type (DAT). This open trial study further examined the relationship of quantitative EEG in relation to treatment response by assessing 24 probable DAT patients at baseline, 2 h after their first oral dose (30 mg), and after 12 weeks of THA treatment. Compared to EEG norms, patients, in general, evidenced EEG slowing, as shown by excessive slow (theta) and diminished fast (alpha and beta) wave power as well as reduced mean frequencies which were present prior to treatment as well as at the end of treatment. The EEG of patients exhibiting stable or improved scores on the Mini-Mental State examination (MMSE) at 12 weeks showed a significantly faster baseline mean alpha frequency as well as a significant reduction in relative theta power following the single THA test dose compared to deteriorated patients. A discriminant analysis using test dose response EEG variables correctly classified 75-79% of these two patient groups, suggesting that this procedure may be a useful approach for optimizing patient selection for antidementia treatments.