A number of new tranquillizing drugs have recently become available. We report a method of assessment for one of these—“Pacatal”. In this experiment the new drug was compared with (i) no treatment at all, (ii) treatment using dummy tablets of the same size and appearance as the Pacatal tablets, and (iii) Largactil. A group of patients suffering from schizophrenia were selected, all being deteriorated. These patients can be found in considerable numbers with a reasonably similar clinical picture which is relatively stationary without treatment.