Among gerontopsychiatric drugs, Hydergine is pharmacologically characterized by agonist action at central dopamine and serotonin receptors. This review presents a summary of the results obtained with Hydergine in numerous controlled trials in patients with senile mental impairment. Assessment was carried out by means of a rating scale (mainly the Sandoz Clinical Assessment Geriatric, or SCAG, scale), psychometric tests (e.g. the Nuremberg Geriatric Inventory, or NGI), and the EEG. Hydergine also lowers serum prolactin, though a correlation with clinical improvement has not been established as yet. In the discussion, the need for objective, measurable and precise indicators in gerontopsychiatry is stressed.