1. Experimental investigations have been carried out with Largactil on chronic and acute mental patients.2. The over-all improvement in chronic cases was 69% and in acute cases 60%.3. However, the transitory effects in acute cases indicate that while Largactil is extremely valuable in chronic psychosis, in acute psychotic breakdowns, it has value only as a sedative.4. Electroencephalogram investigations showed that Largactil markedly decreases the muscle artefacts, decreases the frequency, and increases the voltage, causing a mild progressive synchronization and, in epileptics, it lessens the convulsive threshold.5. In spastics it decreases spasticity through intravenous route, as tested by electromyogram.