The efficacy of the dopaminergic substance Memantine was studied in severe cases of senile dementia of the Alzheimer type using a randomized single blind trial. Following 20 days of a basis therapy, consisting mainly of the proper therapy of medical disorders, 10 patients received 20-30mg Memantine pro die intravenously, 10 other patients were given placebo infusions. Patients were evaluated using the Syndrom Kurztest, the Funktionspsychose-Skala, the Plutchik Geriatric Rating Scale as well as the Sandoz Clinical Assessment Geriatric 5 times following the baseline period. Statistical evaluation showed no significant differences between the two groups. Mild amelioration of sleep-wakefulness cycles and impulse and drive functions could be observed clinically in both groups. Side effects (deterioration of psychopathology in two patients of the Memantine group) disappeared after withdrawal of the substance.